Transport. Pupil Booklet

Transcription

1 Duncanrig Secondary School East Kilbride S3 Physics Elective Transport Pupil Booklet Name: Class: Aspects of the following outcomes in bold are covered by this topic of work. SCN 4-07a I can use appropriate methods to measure, calculate and display graphically the speed of an object, and show how these methods can be used in a selected application. SCN 4-07b By making accurate measurements of speeds and acceleration, I can relate the motion of an object to the forces acting on it and apply this knowledge to transport safety. Learning Outcomes Homework Exercises Unit Summary

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3 S3 Physics Elective Transport Working at Home TO THE PUPIL Each day you have Physics at school, you should set aside time for work at home. By this stage you should be accepting more responsibility for your own learning and should undertake the following tasks on a regular basis: Tackle the supplied homework sheets as each section of work is completed in class. Ensure you meet the deadlines issued by your teacher. Check your own progress in the homework sheets by referring to the homework answer files available in class. Discuss any difficulties that arise with your class teacher. Complete any informal homework tasks that your teacher may issue from time to time and hand them in on the due date for marking. Revise the work you have covered in class activities by referring to your class work jotter and unit summary. Referring to the learning outcomes can also help. Make your own short notes to cover each learning outcome in the supplied study guides. It is your responsibility to catch up on missed work. Use the learning outcomes and summary to help you do this. Speak to your classmates and ask your teacher. Page 1

4 S3 Physics Elective Transport Working at Home Homework Getting Started Success involves doing many kinds of problems which help improve your knowledge and understanding of the content of the course and your ability to solve problems. To get started we will look at a general method for tackling problems. General Method for Solving Problems. Any numerical problem in Physics can be solved using the following steps: Read the question carefully. Find out exactly what is being asked. Extract the key data. Select the correct equation. Substitute the data into the equation and find the missing variable. Give the answer and correct unit. Example How far does a cyclist travel in 26 seconds if she is travelling at a constant speed of 8 metres per second? Solution Read the question carefully Find out exactly what is being asked Distance (how far) Extract the key data time = 26 seconds speed = 8 metres per second Select the correct equation distance = speed x time Substitute data into equation d = 8 x 26 Give the answer and correct unit d = 208 m Page 2

5 S3 Physics Elective Transport Working at Home Usual Layout d =? v = 8 m/s t = 26 s d = v x t = 8 x 26 = 208 m All numerical questions in the following homework exercises should be carried out in this way. No marks will be awarded for an answer given without the working being shown. Helpful Hint Always watch the units in an equation. They may need to be converted before being put into an equation. e.g. 3 ms = s = 3 x 10-3 s 6 km = 6000 m = 6 x 10 3 m Page 3

6 S3 Physics Elective Transport Working at Home FORMULAE FOR THIS UNIT d = vt instantaneous speed = length of mask / time beam is broken thinking distance = speed x reaction time stopping distance = thinking distance + braking distance a = (v u) / t OR v = u + at Page 4

7 S3 Physics Elective Transport Learning Outcomes How Confident am I with the Learning Outcomes? Circle the faces to keep a record of your progress. I am confident that I understand this and I can apply this to problems I have some understanding but I need to revise this some more I don t know this or I need help because I don t understand it You can use this to help you pick the areas of the unit that need the most revision. As you revise your class work you will be able to circle more and more smiley faces. If that does not help then you should ask your teacher! Learning Outcomes 1. State that speed is the distance covered per unit of time. 2. Use the formula d = vt to calculate average speed. Can you do this? 3. Describe how to measure average speed. 4. Describe a road safety application where average speed is calculated. 5. State that the stopping distance for a vehicle is the sum of the thinking distance and braking distance. 6. State that thinking distance is the distance covered by a vehicle while the brain is processing (before the brakes are applied). Comments Page 5

8 S3 Physics Elective Transport Learning Outcomes 7. Use the formula d = vt to calculate the thinking distance (where v is the speed of the vehicle and t is the thinking/reaction time) 8. Know various factors that can affect reaction (thinking) times. 9. State that the braking distance is the distance covered by a vehicle while coming to a stop (after the brakes are applied) 10. Know various factors that affect the braking distance. 11. Use the formula d = vt to calculate instantaneous speed (where v is the instantaneous speed, d is the length of the mask, and t is the time the beam is broken) 12. Describe how to measure instantaneous speed. 13. Know the difference between average speed and instantaneous speed. 14. Describe a road safety application where instantaneous speed is calculated. 15. State that the definition for acceleration is the change in speed per second measured in metres per second per second (m/s 2 ). 16. Use a = (v-u)/t OR v = u + at in acceleration and deceleration calculations. 17. Describe a method for measuring acceleration experimentally. Page 6

9 S3 Physics Elective Transport Learning Outcomes 18. Convert quantities to appropriate units prior to using formula. 19. Describe a road safety application where acceleration is calculated. 20. State that if the time of impact of a collision is longer the deceleration is less. 21. Crumple zones can increase the time of impact in a crash and absorb the energy from the impact. Page 7

10 Answer the questions in this homework, where appropriate in full sentences, on the blank page that follows. Transport Homework 1 Average Speed and Cameras 1. Jane jogs to work every day at an average speed of 4 m/s. Most days it takes her 600 s to reach work. Calculate how far she jogs. (2) 2. A top class sprinter covers the 100 m in a time of 10 s. Calculate the sprinter's average speed. (2) 3. How long will it take a Formula 1 car to travel one lap around a 5 km long circuit if it is travelling at an average speed of 180 km/h? (2) 4. In a school experiment, a small trolley is allowed to run down a ramp. (a) Describe how the average speed of the trolley could be measured. (3) (b) During one run the trolley is found to take 2.5 s to travel between the lines which are 0.8 m apart. Find the average speed of the trolley. (2) 5. An average speed camera on the M77 records a vehicle passing an entrance camera at pm. When the number plate is digitally recorded leaving the exit camera the time is pm. Show whether the vehicle was speeding if the distance between the entrance camera and exit camera was 4 km and the speed limit on the road was 60 m.p.h. (3) (Note: to convert from m/s to m.p.h. multiply by 2.24) Total 14 marks Page 8

11 Complete Homework 1 Average Speed and Cameras below. Page 9

12 Answer the questions in this homework, where appropriate in full sentences, on the blank page that follows. Transport Homework 2 Reaction Times and Stopping Distances 1. Use the diagram below to answer questions (a) and (b). (a) You are travelling at 30 m.p.h. in good road conditions when you suddenly see children crossing the road, what would be the overall stopping distance for your car? (1) (b) What happens to the stopping distances when the speed of the car increases? (1) (c) What is meant by the term thinking distance? (1) (d) What would happen to your thinking distance if you were driving when tired? Why would this happen? (2) (e) If your car is going faster will your reaction time alter? Explain your answer. (2) 2. Calculate the thinking distance for the data in the table below. Thinking/Reaction Time (ms) Speed of vehicle (m/s) (Note: to convert from ms to s divide by 1000) (6) Total 13 marks Page 10

13 Complete Homework 2 - Reaction Time and Stopping Distances below. Page 11

14 Answer the questions in this homework, where appropriate in full sentences, on the blank page that follows. Transport Homework 3 Instantaneous Speed and Cameras 1. A bike is travelling along a cycle track. (a) Describe how you could measure the instantaneous speed of the bike. (3) (b) If the bike took 0.5 s to pass a horizontal line of the track and the length of the bike was 2 m, calculate the instantaneous speed of the bike. (2) 2. A coin is dropped from a height so that it passes through a light gate connected to a computer. The coin has a width of 0.02 m and it takes 0.05 s to pass through the light gate. Find its instantaneous speed. (2) 3. What is the name of the device on a vehicle that displays the instantaneous speed? (1) 4. A driver receives a speeding fine as when he drove through a speed trap he covered 7.62 m in 0.3 s. (a) Calculate his speed in m/s. (2) (b) Convert his speed to m.p.h. (multiply by 2.24). (1) (c) Suggest a possible speed limit for the road he was driving. (1) Total 12 marks Page 12

15 Complete Homework 3 - Instantaneous Speed and Cameras below. Page 13

16 Speed (m/s) Answer the questions in this homework, where appropriate in full sentences, on the blank page that follows. Transport Homework 4 Acceleration 1. What is the definition of acceleration? (1) 2. The table below shows the performance figures for some makes of car. Which row in the table shows the car that will go from 0 60 m.p.h in the shortest time? (1) Car Top speed (mph) Acceleration (mph per second) A B C D Calculate the acceleration of a car that increases its speed by 10 m/s in 5 s. (2) 4. Calculate the final speed of a train which accelerates uniformly at a rate of 0.6 m/s 2 from a speed of 2 m/s for 30 s. (2) 5. A motorbike can accelerate from 10 m/s to 26 m/s in 8 s. Calculate its acceleration. (2) 6. Calculate the deceleration of a car with initial velocity 30 m/s which comes to rest in 15 s. (2) 7. Use the values from the speed/time graph below to calculate the acceleration of the vehicle. (2) Speed/Time Graph Time (s) Total 12 marks Page 14

17 Complete Homework 4 - Acceleration below. Page 15

18 Answer the questions in this homework, where appropriate in full sentences, on the blank page that follows. Transport Homework 5 Test Preparation 1. If you have not already done so work your way through the learning outcomes, at the front of this booklet, circling the appropriate face. Make sure you are referring to your jotter and summary notes as you work your way through each one. Speak to your classmates and teacher to help you with weaker areas. 2. Revise the unit summary. It may be helpful to draw a mind map, highlight the notes, or write your own. It is important that you do more than just reading. 3. For each section in the summary design a question that could be asked in the exam. Write down your question and answer in the following form. e.g. Section Reaction Times and Stopping Distances Question Name a factor that affects human reaction time. Answer Alcohol levels. 4. Practise your numerical work by answering the following questions. (a) (b) (c) (d) (e) (f) A toy car covers a distance of 0.6 m in a time of 2 s. Calculate the average speed of the car. (2) A football of diameter 20 cm cuts a light beam for 0.25 s. Calculate the instantaneous speed of the ball. (2) Calculate the thinking distance if the driver s reaction time is 0.7 s and he is travelling at a speed of 20 m/s. (2) A motorcycle accelerates constantly from 20 m/s to 35 m/s in a time of 3 s. Calculate the acceleration of the motorbike. (2) Calculate the final speed of a car if it accelerates at 4 m/s 2 for 5 s. Its initial speed was 10 m/s. (2) A lorry driver brakes and decelerates at a constant rate from 12 m/s to 4 m/s in a time of 4 s. Calculate the deceleration. (2) Page 16

19 Complete Homework 5 - Test Preparation below (if appropriate). Page 17

20 The unit summary is provided to help supplement your class notes and should be used when completing homework and studying for the test. Along with the learning outcomes, it can be used to help you catch up on missed work. Unit Summary Section 1 Average Speed Speed Definition The speed of an object is a measure of the distance covered in a unit of time, for example a speed of 50 m/s means that the object travels 50 m each second or 60 km/h means the object travels 60 km every hour. Calculating Average Speed Average speed is a measurement of speed that takes into account that the object may have accelerated, decelerated, travelled at different constant speeds, and could even have stopped during the journey. Therefore, it is an average for the whole journey. We can calculate the average speed of an object using the formula d = vt where: d represents distance v represents the average speed t represents time Using the Correct Units for Speed Calculations It is important to consider your units when calculating speeds. The units you use for speed can be determined from your units for distance and time. Page 18

21 The unit summary is provided to help supplement your class notes and should be used when completing homework and studying for the test. Along with the learning outcomes, it can be used to help you catch up on missed work. If d is measured in metres (m) and time is measured in seconds (s) then the speed is measured in kilometres (km) hours (h) miles (M or m.) hours (H or h) metres per second (m/s) kilometres per hour (km/h) miles per hour (MPH or m.p.h.) Sometimes there is the need to convert from one unit to another. e.g. 3 ms = s = 3 x 10-3 s 6 km = 6000 m = 6 x 10 3 m Using d = vt to Calculate Average Speed This is how to calculate the average speed if the vehicle took 30s to travel 150m. d = 150 m v =? t = 30 s d = v x t 150= v x 30 v = 150 / 30 = 50 m/s Describing a Method for Measuring Average Speed Measure the distance the object travelled using a tape measure. Measure the time taken to travel that distance using a stopwatch. Use the formula d = vt to calculate the average speed. Page 19

22 The unit summary is provided to help supplement your class notes and should be used when completing homework and studying for the test. Along with the learning outcomes, it can be used to help you catch up on missed work. Average Speed Cameras Some roads have average speed cameras along their length. As vehicles pass between the entry and exit camera points their number plates are digitally recorded, whether speeding or not. Then, by Automatic Number Plate Recognition (ANPR), the images on the video of matching number plates are paired up, and because each image carries a date and time stamp, the computer can then work out the average speed between the cameras using the formula d = vt. Section 2 - Reaction Time and Stopping Distances Reaction Time and Stopping Distances When a vehicle stops there are two factors that contribute to the stopping distance: 1. The thinking distance which is the distance covered by the moving vehicle while the driver s brain is processing that he needs to stop (before the brakes are applied). 2. The braking distance which is the distance covered once the brakes are applied. Stopping distance = thinking distance + braking distance. The thinking distance can be calculated from the formula d = vt, where v is the speed of the vehicle and t is the thinking time (or reaction time). This means that if the speed and/or reaction time increases, so does the thinking distance. Page 20

23 The unit summary is provided to help supplement your class notes and should be used when completing homework and studying for the test. Along with the learning outcomes, it can be used to help you catch up on missed work. Reaction times increase if a driver has been drinking, taking drugs, and/or is tired. In addition, if the driver is distracted by using a mobile phone or changing music this will also increase their reaction time. The diagram below shows typical stopping distance at speeds from 20m.p.h. to 70m.p.h. illustrating that an increase in speed increases the thinking, braking, and overall stopping distances. If the roads are wet or icy braking distances increase. The Venn diagram below shows how various factors can affect thinking and braking distances. Page 21

24 The unit summary is provided to help supplement your class notes and should be used when completing homework and studying for the test. Along with the learning outcomes, it can be used to help you catch up on missed work. Section 3 - Instantaneous Speed Instantaneous Speed The instantaneous speed is the speed of the vehicle at that instant. The speedometer on a car displays the instantaneous speed. To calculate instantaneous speed the time recorded must be very short; this can be done by making the distance very short, for example, the length of the vehicle or something on the vehicle (a card/mask). Since the time measured is very short human reaction time can adversely affect this value of time. To stop human reaction time affecting time measurements a light gate connected to a computer (set to be a timer) can be used. In this situation the d = vt equation becomes: instantaneous speed = length of mask / time beam is broken Using d = vt to Calculate Instantaneous Speed This is how to calculate the instantaneous speed of a vehicle of length 4m that took 0.5s to pass a horizontal line on the road. d = 4 m v =? t = 0.5 s d = v x t 4= v x 0.5 v = 4 / 0.5 = 8 m/s Describing a Method for Measuring Instantaneous Speed Measure the length of the object (or mask on the object) using a ruler. Allow the object to cut the beam of a light gate and record the time the beam is broken from the timer. Use the formula d = vt to calculate instantaneous speed where d is the length of the object and t is the time the beam is broken for. Page 22

25 The unit summary is provided to help supplement your class notes and should be used when completing homework and studying for the test. Along with the learning outcomes, it can be used to help you catch up on missed work. Instantaneous Speed Cameras There are many types of instantaneous speed cameras designed to monitor that drivers are observing the speed limit. The Gatso speed camera projects a radar beam onto your vehicle which tracks your speed. If it senses you're driving above the limit then it takes 2 photos, the second photo is taken a fraction of a second after the first. Drivers are warned that they are approaching a speed camera by the speed camera sign. They will also see white lines on the road, this indicates the have entered the speed trap area. These white line markings on the road surface provide a secondary method of calculating the drivers speed using d = vt, where d = the distance between the markings and t = the time to cover that distance. Section 4 - Acceleration Definition of Acceleration Acceleration is the change in speed per unit of time. If the speed is measured in m/s and the time in s then the units for acceleration are m/s 2. Acceleration Formula Acceleration can be calculated from the formula a = v u / t where: a represents acceleration v represents the final speed u represents the initial speed t represents time Page 23

26 Speed (m/s) (m/s) The unit summary is provided to help supplement your class notes and should be used when completing homework and studying for the test. Along with the learning outcomes, it can be used to help you catch up on missed work. However, it can be easier to work with this formula in the form v = u + at if you have been asked to calculate v, u, or t. Using a = v u / t to Calculate Acceleration This is how to calculate the acceleration of an object initially at rest whose speed increases to 20 m/s in 4 s. a =? u = 0 m/s v = 20 m/s t = 4 s a = v u / t = 20 0 / 4 = 20 / 4 = 5 m/s 2 Using v = u + at to Calculate Final Speed This is how to calculate the final speed of an object accelerating at 2 m/s 2 from 10 m/s in a time of 8 s. a = 2 m/s 2 u = 10 m/s v =? t = 8 s v = u + at = (8) = 26 m/s Calculating Acceleration from a Speed/Time Graph Sometimes the information needed to calculate acceleration can be presented on a graph. 60 a =? u = 0 m/s v = 50 m/s t = 5 s a = v u / t = 50 0 / 5 = 50 / 5 = 10 m/s Time (s) Page 24

27 The unit summary is provided to help supplement your class notes and should be used when completing homework and studying for the test. Along with the learning outcomes, it can be used to help you catch up on missed work. Deceleration A negative acceleration is referred to as deceleration and can be calculated from the formula a = v u / t. Using a = v u / t to Calculate Deceleration This is how to calculate the deceleration of a vehicle travelling at 15 m/s which slows to 5 m/s in a time of 4 s. a =? u = 15 m/s v = 5 m/s t = 4 s a = v - u / t = 5 15 / 4 = -10 / 4 = -2.5 m/s 2 A Method to Measure Acceleration Experimentally The following experimental set up can be used to measure the acceleration of a trolley running down a slope. Set the computers to measure speed. Input the length of the mask. As the mask on the trolley cuts the first light gate, then the second, the computers calculate the initial and final speeds using instantaneous speed = length of mask / time beam is broken. The stop clock is used to time how long it takes the trolley to run from the first to second light gate. The formula a = v u / t is used to calculate the acceleration. Mask on trolley Computer Computer Slope Light gate Stop clock Page 25

28 The unit summary is provided to help supplement your class notes and should be used when completing homework and studying for the test. Along with the learning outcomes, it can be used to help you catch up on missed work. Section 5 Crumple Zones Crumple Zones Crumple zones on cars are designed to absorb the impact of a crash so as to protect the occupants inside. They also make the time of impact of a crash longer as this reduces the deceleration. Crumple zones can be on the front, back and even the sides of vehicles. Euro NCAP organizes crash-tests to assess the safety of some of the most popular cars sold in Europe. One of the tests they carry out is on crumple zones to see how effective they are at protecting the occupants. The crumple zone is sacrificed in a car crash in order to keep the passenger compartment intact. Page 26

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