How a force causes movement? What is Newton s first law of motion? Newton s first law of motion The ingenious English mathematician and physicist Sir Isaac Newton (164-177) was the first to fully understand how objects actually move, expressing his three famous laws of motion. or this and many other discoveries he is recognised as one of the most influential scientists of all times. Place the model on a flat surface. Obviously it does not move by itself. Explain why in exercise. Place the cabin in the middle and move your vehicle smoothly, holding it by the large rod on the edge. Observe how the cabin moves and answer question Explain why the model stands still in step of the experiment in reference to the sum of forces applied. The model is not moving because there is no force acting on it big 5. or the final test, you are going to imitate an accident. Place the cabin on one edge and push the vehicle sharply from the large rod onto a wall or any other strong obstacle. Be careful not to push too hard and have pieces flying around, as there is a risk of injury! Make sure you pick up any falling pieces. Write your observations about the vehicle and how the cabin moved in exercise 4. 6. Read carefully Newton s first law of motion on the right and explain all your findings according to it about the cabin s motion in exercise 5. - Long rubber band and measure tape. When the model is moving smoothly in step, how does the cabin move? Draw the sum of forces in the picture below. place cabin in the middle Complete the table according to your measurements from the experiment. Projectile (number of wheels) When the vehicle is moving smoothly, the cabin also moves along the middle of the model.. When the model is pushed sharply in step 4, how does the cabin move? When the vehicle is pushed sharply, the cabin moves to the back side of it. 4. What happens to the vehicle when you push it onto to the wall in step 5? How does the cabin move this time? When the vehicle is pushed onto a hard object, it stops completely and some pieces fall off. The cabin moves to the front of the vehicle. 5. Read Newton s first law of motion and discuss your findings according to it about the cabin s movement in steps,, 4 and 5. In steps and, the velocity is zero or constant, so the cabin stays in the middle. In steps 4 and 5, the force is sudden and the cabin ind the instructions in pages 6-8 and build the ballistic catapult model. Pass the rubber band twice through the holes and tie it in the end. or safety reasons, is better you conduct the experiment outdoors and make sure noone is standing in front of the catapult when is loaded and ready to shoot. Also, be careful with the rubber band as it can break under high tension.. In all launches is important that two factors are kept constant: the tension of the rubber band and the shooting point. 4. or test 1, place your catapult at a fixed point and load it with one wheel-pulley assembly (as shown in the table, projectile column). Hold the catapult with one hand and release the medium rod. A second person is required to see the exact point where the projectile touched first. With the help of a measure tape, find the distance between the catapult and that point and write it on the table (1a). Repeat the same procedure two more times and write the results for 1b and 1c. Then calculate the average distance by adding the together and dividing by. to keep this state by staying back. In step 5, the cabin is 15 moving forward and tries to keep this after the hit. Average distance (m) 1 66 61 6 0 4 7 7 0.70. 0.74 0.76 0.84 Compare the average distances in all tests. What do you observe? The results show that the lighter the projectile (e.g. one wheel) the larger average distance it covers and vice versa.. Read about Newton s second law of motion below and explain your observations from the experiment. Keep in mind that the force (rubber band s tension) is the same in all cases. Newton s second law of motion: The sum of forces acting on an object is equal to the mass m of the object multiplied by the acceleration a of the object. = m.a According to the observations above, as force is constant, mass and acceleration are inversely proportional to each other. 5. or test and test, add one and two wheel-pulley assemblies and repeat the same as before. Write the results in a, b, c and a, b, c and calculate the average distances wants to keep its velocity. This unwillingness to move in sudden changes is called inertia. So, in step 4, the cabin is at rest and wants Projectile s distance (m) 54 move vehicle from the large rod Newton s first law of motion: Every object remains at rest or continues to move at a constant velocity, unless acted upon by an external force. Push the model onto a wall and observe the cabin s movement. What is Newton s second law of motion? How force acting upon an object is related to the object s mass and acceleration? words the sum of forces applied equals to zero or is very weak. with it in a smooth way. Therefore it stays in the same place, thus 4. Keep the cabin in the middle and push the vehicle sharply this time. Observe again how the cabin moves and answer question. Newton s second law of motion Another great scientist contributed to the discovery of the properties of forces and acceleration long before Newton s time: the Italian physicist Galileo Galilei (1564-164). He was rolling balls down various inclined planes and came up with formulas, which were finally explained by Newton centuries after! enough to exceed its inertia (mass) and set it into motion. In other ind the instructions in pages 4-5 and build the moving cabin model. 6. Answer all the questions that follow. When you finish do not disassemble your model, as you will need it for the next experiment also. 16
What is Newton s third law of motion? What is an equal and opposite force? Newton s third law of motion Newton s third law of motion is so simple that is surprising how many years it took to be formulated! It is applicable in all situations that forces are involved! The third law explains why balls bounce, why we feel pain when we hit our hand on the table and how rockets can escape Earth s gravitational pull! - Long rubber band. - 6 cylindrical pencils and ruler. - Bag with sand and weigh scale. Complete the table according to your measurements from the experiment. Projectile s weight (g) ind the instructions in pages 6-8 and build the ballistic catapult or use the one from the previous experiment without the wheels. Pass the rubber band twice through the holes and tie it in the end. or safety reasons, is better you conduct the experiment outdoors and make sure noone is standing in front of the catapult when is loaded and ready to shoot. Also, be careful with the rubber band as it can break under high tension.. In all launches it is important that two factors are kept constant: the tension of the rubber band and the shooting point. Catapult s distance (cm) 50 g This assembly is around 5 g and you can use it alternatively to the bag with sand, for small weights. 100 g 5. 00 g start measuring the catapult s distance from this point (the last pencil) Compare the measurements from all tests. What do you observe? The results show that the heavier the projectile, the longer the catapult is moving backwards (shown by catapult s distance column) and vice versa. 4. ind a fixed point and set your model above 6 cylindrical pencils (as shown in the picture). Alternatively, you can place your model in a slippery place. 5. or test 1, fill the bag with 50 grams of sand, measured with the weight scale. Alternatively you can use Engino wheelpulley assemblies (see picture on the right) or other materials. Place your ruler on the edge of the model (last pencil) and shoot the projectile. Then measure how much distance the catapult has moved after the launch and write it on the table in exercise 6. Repeat the same procedure for tests and, altering the weight 100g and 00g. 7. Answer the questions that follow according to your results and Newton s rd law. Momentum A Newton s cradle is a device that consists of a few metal balls (usually 5) hanging freely from threads on a metal base. When one ball is pulled and let free to hit the second ball, something strange happens: the last ball moves instead of the others. ind out why by conducting the next experiment. - Rubber band. ind the instructions in pages 9-0 and build the collision car model. Note that the seats move freely inside the car. Take the Engino string and tie its one end on the back side of the vehicle and the other end on a fixed point (e.g. a table s leg)..5. Read Newton s third law of motion and explain your findings according to it, about the relation between the projectile s weight and the catapult s distance. Newton s third law of motion: or every action there is an equal and opposite reaction. The catapult applies a force to the projectile. In turn, the projectile. Push the vehicle with low force and let it move until stopped by the string. Observe how the seats behave and answer exercise 4. Push the vehicle with much more force this time (sudden push) and let it move again until is stopped by the string. Write how the seats behave this time in exercise 5. With the seats inside the vehicle, take a rubber band and place it around them, from the steering wheel to the grey part s end. Connect an orange part with it so it has a better grip. This way you will create a seat belt. Push again with strong force as in step 4 and observe what happens to the seats. Explain your findings and the importance of fastening your seat belt in exercise. What is Momentum? What is the formula for calculating Momentum? What do you observe about the seats of the model when you push with low force? When the model is pushed with low force, the seats move a bit but they stay inside the vehicle. What do you observe about the seats of the model when you push with strong force? When the vehicle is pushed with strong force, the seats move faster than before and eventually jump out of the vehicle.. What do you observe about the seats fastened with seat belt when you push with strong force? How important it is to fasten your seat belt while travelling inside a vehicle? The passengers are more safe with the seat belt! The seats stay inside the vehicle even if a very strong force is applied. astening the seat belt is very important, as it holds the passengers when the car stops abruptly, saving them from fatal injuries. 4. Why the seats of the model behave differently in each case? Take into consideration the momentum formula below. 6. This experiment is based on Newton s laws of motion and momentum. Explain your findings according to them in exercise 4. Momentum p is the product of the mass m and the velocity v of an object. p = m.v The momentum of the vehicle is transferred to the seats and is applies an equal and opposite force, causing the catapult to go back. proportional to the velocity of the model. With low force, the seats do 4. Why the projectile travels longer distance in comparison with the catapult? The force of the projectile and the catapult is the same. As force is not have enough momentum to escape the car. But, with larger force Newton s cradle the seats jump out of the vehicle due to larger momentum. The seat belt cancels the seats momentum by applying elastic force back. proportional to mass and acceleration (second law), the heavier catapult travels less distance than the lighter projectile. 17 18
What are the fundamental properties of? How does change forms? Properties of Everyday we observe so many little changes in our surrounding environment that we neglect most of them: people walking, cars moving, electrical devices working, dogs barking. All these tasks have a common factor: they require in order to execute them. Explore and its properties below. - Balloon. Complete the table according to your measurements from the experiment. Air inside the balloon Aeroplane s stop time (s) Average stop time (s) 1 ind the instructions in pages 1- and build the balloon powered plane. Place it on the floor, free of any obstacles around it. The balloon should be placed on the last hole of the long side (opposite the plane) as shown in the picture. ill the balloon with air, twist its loose end a couple of times so there is no air loss and place its ring around an Engino ring part. Connect the ring with the last hole of the last medium rod.. or test 1, fill the balloon with big blows of air (be careful not to burst it) and place it as described above. or the test two people are needed: one should let the air blow out of the balloon. At that moment, another person should start the stopwatch and measure how much time is needed until the plane stops turning. Write the time in (1a) in the next table. Repeat the same procedure for (1b) and (1c). Then calculate the average stop time by adding the measurements together and dividing by. big blows 11 1 1 1 big blow 5 4 Compare the average stop times of both tests. What do you observe? What factor changed so that the times differ? The results show that the bigger the balloon, the more time is needed for the aeroplane to stop rotating. The factor that changed is the air inside the balloon.. Read the properties of below and describe your observations according to them. Make sure you refer to the different transformations as well as to storage. Properties of : Energy is conserved over time and cannot be created anew or destroyed. through the interaction of forces between the objects. etc.) and it is converted from one form into the other. The balloon stores wind and elastic. When the air is released, its is converted into kinetic, which turns the aeroplane. 5. Read about the properties of and explain your observations in question. The model stops not because the is lost, but because is Place the ring of the air-filled ballon around the Engino ring Potential and Kinetic energies Energy comes in various forms. But, the two most common forms of, involved almost in all transformations are potential and kinetic. Probably you will think that they depend on many factors, but you will be surprised to know that both can be calculated with the use of two very simple formulas. ind the instructions in pages 4-6 and build the gravity fan. Place its legs between two tables, so the wheels can drop freely. converted into other forms due to air resistance and friction. 19 Complete the drop speed column by using the words: slow, medium and fast according to your observations in test Write your conclusions below in relation to weight, speed and, considering that all other factors are constant. or test 1, the load factor (number of wheels) will be changing and the height factor will remain the same, that is the top of the fan (100%), in all cases (1-).. or case 1, place 1 wheel and wind up the string, by turning the blades, until it reaches the top of the fan. Release the load and observe how fast the wheel reaches the ground. Repeat the same procedure for cases and, adding another wheel each time. Observe again the drop speed of the wheels and complete the table in exercise 1 by using the words: slow, medium and fast, as well as your conclusions from the test. 4. or test, the height factor will be changing and the load factor will remain the same. Place the ring with the balloon on the last hole of the medium rod. 5. or case 4, place 4 wheels and wind up the string until the fan reaches the top. Let the load drop and observe the speed of the fan. More specifically, observe how much acceleration is achieved and for how long. Keep the same load for cases 5 and 6 but let it drop from 50% of the height (measured from the ground to the top of the fan) and 5% respectively. Complete the table with the words: short, medium and long and write your conclusions from the test in exercise 6. Answer question about the main forms of energies involved in both tests and their formulas. The heavier the load the faster TEST 1 Case Load (number Drop speed of wheels) the drop speed of the wheels. This shows that the weight of an 1 slow object affects directly the speed (and time) needed for the object medium to drop to the ground. If heavier means faster, then we can conclude that more mass. fast means more. Complete the fan s time of acceleration column by using the words: short, medium and long according to your observations in test Then write your conclusions in the space provided in relation to the height, acceleration and, when all other factors are constant. TEST Case Dropping height Energy can be stored and transferred from one object to another. Energy comes in a variety of forms (kinetic, potential, sound, heat 4. or test, fill the balloon with less air, that is 1 big blow. Repeat the same procedure as step and write your findings in a, b and c, as well as the average stop time. Then compare the two average times of both tests and explain why they differ in question What is potential and kinetic and how are they connected? What are their formulas? 4 The higher we place the load, an s time of the longer the fan is acceleration accelerating. This shows that 100% (top) long 4. the height in which an object is placed affects directly its 50% medium 5. acceleration (and speed). If higher means more acceleration, then we can conclude that 5% short 6. higher means more.. In both tests, which main forms of energies are involved and what are their mathematical formulas? We see a conversion from potential into kinetic. Potential is PE = m.g.h and Kinetic is KE = 1/m.v, 0 v = velocity, m = mass and g = gravitational acceleration.
Exercise Quiz Can you draw and label all the forces acting on the car which is moving uphill? Consider the air resistance as negligible (points ) Exercise 1 N In the pictures below you can observe various forms of. Choose the correct one from the box, the main form of depicted in each picture and write it in the space provided (points ) kinetic, electric, chemical, light, sound, elastic, gravitational, thermal, magnetic f W Label the forces here: : force that causes the car to move (applied from the engine). N : normal force (applied from the ground). W : force of the weight of the car. f : force of friction (between the tires and the ground). Exercise Write the three properties of ( points) acoustic thermal elastic 1) Energy is conserved over time and cannot be created anew or destroyed. ) Energy can be stored and transferred from one object to another through the interaction of forces between the objects. ) Energy comes in a variety of forms (kinetic, potential, sound, heat etc.) and it is converted from one form into the other. Exercise 4 Explain according to Newton s laws of motion why seat belts and airbags are essential for avoiding fatal injuries in car accidents (points ) electric chemical kinetic During big accidents with great speeds, cars are stopped abruptly. The passengers... inside the car, who are moving with the same speed as the car, want to keep this... speed because of inertia. So, they continue moving towards the windshield even if the... car is stopped. If there were not any seat belts or airbags to cancel out their... momentum, then the passengers would hit the glass hard, resulting in fatal injuries....... Exercise 5 In the picture on the right a boy is pushing against the wall. Draw the forces involved and describe Newton s law of motion that applies in this case. (points ) light magnetic gravitational In this case, Newton s third law of motion applies. When the boy is pushing against... the wall applying a force, at the same time the wall is pushing the boy back with an... equal and opposite force....... 1
Exercise 6 a) Write Newton s second law of motion and its formula. (points ) Newton s second law of motion states that: the sum of forces acting on an object is equal to the mass m of the object multiplied by the acceleration a of the object. Mathematically this is expressed by the formula = m. a b) A cannon fires an iron ball weighing 15 kg with a force of 000 N. What is the ball s acceleration just after it leaves the cannon s barrel? (points ) According to Newton s second law of motion:. = m. a _ a = _ a = 000 _ a = 00 m/s. m 15. So, the ball exits the barrel with an acceleration of 00 m/s.. Exercise 7 a) Can you briefly describe the following pictures in relation to the notion of momentum and the law of conservation of momentum? (points ) All pictures are examples of momentum transferring. The objects that are firstly set into motion (white ball, bowling ball and iron ball) gain momentum from their mass and speed due to the force applied. When they get in contact with other objects, they transfer their momentum and set these into motion as well, but still maintaining the initial momentum of the system. b) i) A car is moving at 7 km/h and weighs 1500 kg. What is its momentum? ii) What velocity theoretically should a golf ball have, weighing 0,1 kilograms, in order to achieve the same momentum as the car? (points ) i) All units should be converted into the SI metric system:... vcar = 7 km/h = 7000 m / (60. 60 ) _ vcar = 0 m/s... pcar = mcar. vcar = 1500. 0 _ pcar = 0000 kg.m/s... ii) pball = pcar _ mball. vball = pcar _ vball = pcar / mball _ vball = 0000 / 0,1 = 00000 m/s... Visit our online resources to find the solutions of all the activities: www.engino.com/solutions/stem07