Review. 8th grade science STAAR. Name Class. Underline your strong TEKS and circle your weak TEKS: 8.6A Unbalanced Forces

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1 8th grade science STAAR Review Name Class Underline your strong TEKS and circle your weak TEKS: 8.6A Unbalanced Forces 8.6B Speed, Velocity, & Acceleration 8.6C Newton s Laws 7.7A Work 6.8A Potential and Kinetic Energy 6.8C Speed 6.8D Graphing Motion 6.9C Energy Transformations 2014 Science Teaching Junkie, Inc. 1

2 Reporting Category 2: Force, Motion and Energy Unbalanced Forces 8.6A A is a push or a pull in a specific direction. The combination of all of the forces acting on an object is called. Determine the net force (size and direction) for the following: 2N 5N 2N 2N 5N 5N Net force= Balanced or unbalanced? Net force= Balanced or unbalanced? Net force= Balanced or unbalanced? If the forces acting on a moving object are balanced, what will the object do? If the forces acting on an object at rest are balanced, what will the object do? If the forces acting on a moving object are unbalanced, what will the object do? If the forces acting on an object at rest are unbalanced, what will the object do? Force is measured in what units? Friction is a force. How does friction affect the speed of a moving object? 3.0 m/s 8.5 m/s A submarine is traveling in the water at 8.5 m/s. Suddenly the sub encounters a swiftly moving current. If the current is flowing against the submarine at 3.0 m/s how will the sub be affected? 2014 Science Teaching Junkie, Inc. 2

3 A diagram of the forces being applied to a box is provided (below). If the net force acting on the box is 10 N to the right, what is the magnitude of the force applied by the boy pulling to the left? Record your answer in the grid below. Show all work! Which of the following objects requires the greatest amount of force to produce the acceleration shown? Object Acceleration (m/s 2 ) Mass (kg) Object A Object B Object C Object D A student applies 2 Newtons of force to a toy car causing it to accelerate at a rate of 10 m/s 2. What is the mass of the toy car in kg? Record your answer in the grid below. Show all work! 2014 Science Teaching Junkie, Inc. 3

4 Speed, Velocity, & Acceleration 8.6B What is speed? Average speed = What is velocity? What is acceleration? Identify each of the examples as either a speed (S), velocity (V), or acceleration (A). A rollercoaster slows as it travels up a hill. A cyclist travels 40 kilometers in 2 hours. A flock of geese flies north at 55 mph. A racecar makes a slight left turn while maintaining the same speed. An athlete can run about 12.5 km/hr. A car travels 2.5 hours in a northerly direction for 300 km. Determine the car s speed and velocity. Show all work! Speed = Velocity = Study the diagram below. A student rides a bike 2 hours from school to home, making stops along the way. What is the average speed that the student is traveling? 4 km friend s house 3 km library 2 km Did the student accelerate during the ride home? school home 2014 Science Teaching Junkie, Inc. 4

5 Newton s Laws 8.6C Newton s Law of Motion states that for every action, there is an equal and opposite reaction. Forces come in pairs. It is often referred to as the law of action-reaction. Newton s Law of Motion states that an object at rest will stay at rest and an object in motion will stay in motion at the same speed and in the same direction unless acted up by an unbalanced force. It is sometimes called the law of inertia. Newton s Law of Motion states that an object acted upon by an unbalanced force will accelerate in the direction of that force, in direct proportion to the strength of the force, and in inverse proportion to the mass of the object. It is called the law of force and acceleration. Define inertia and give an example. What formula is used for Newton s Second Law of Motion? State the 3 forms of the formula. Check One First Law of Motion Second Law of Motion Third Law of Motion 2014 Science Teaching Junkie, Inc. 5

6 If a team pulls with a combined force of 9000 N on an airplane with a mass of 30,000 kg, what is the acceleration of the airplane in m/s 2? Record your answer in the grid below. Show all work! tennis racket and ball m = 1.0 kg variety of sport balls m = 12 kg 2 bowling balls m = 25 kg The shopping carts shown above are pushed down the hallway with the same amount of force. Which cart has the greatest change in speed? Circle the cart above and explain your answer below. Work 7.7A In science, for work to be performed, a force must be used to move an object. Regardless of how much force is being used, if no movement occurs, no work is done. Work = x Work is measured in a unit called ( ). The man in the picture is pushing against the beach ball with 20 Newtons of force. The ball does not move. How much work is he doing? Show all work! 2014 Science Teaching Junkie, Inc. 6

7 Example #2 work Use the information and diagrams below to answer the 2 questions that follow. A student needs to lift a heavy ball up onto a table that is 2 meters high. She uses 6 N of force to raise the ball straight up (Ex. #1), but only 3 Newtons of force is required to roll the ball up the ramp (Ex. #2). d = 4 m F = 6 N 2 m F = 3 N 2 m Example #1 Example #2 Calculate the amount of work done for each example above. Show all work! Example #1 work Does the amount of work change in the two examples? Explain. Which of the following results in the least amount of work being done? A. A dog carries a toy 2 m with a force of 1 N. B. A child moves a ball 3 m with a force of 4 N. C. A student pushes a book with a force of 5 N for 1 m. D. A coyote drags its prey with a force of 20 N for a distance of 5 m. Potential and Kinetic Energy 6.8A Fill in the data table (right) to correctly classify the activities of the children in the picture as either kinetic (K) or potential (P) energy. Activity Observed Girl jumping rope Boy standing with a soccer ball Kite flying in the wind Boy balancing on his head Bee buzzing around a boy s head Classification 2014 Science Teaching Junkie, Inc. 7

8 2 1 At which point does the water in the waterfall (left) have the greatest gravitational potential energy? Circle your answer in the picture. 4 3 Use the diagram of the rollercoaster above to fill in the missing information. a) As the rollercoaster moves from point Z to point Y, the potential energy as the kinetic energy. b) As the rollercoaster moves from point Y to point X, the potential energy as the kinetic energy. c) At which of the 4 points does the cart have the least potential energy? A diagram of a pendulum is shown to the left. The pendulum is released from Position 1. At which two positions will the pendulum s potential energy equal its kinetic energy? A. 1 and 2 B. 2 and 4 C. 3 and 4 D. 4 and 5 is energy that is stored and available to be used later. is energy that an object has because of its motion Science Teaching Junkie, Inc. 8

9 Speed 6.8C If an object travels 42 meters in 6 seconds, what is its average speed? A. 6 m/s B. 7 m/s C. 48 m/s D. 252 m/s What is the difference in average speed between two cars, one that traveled 150 kilometers in 5 hours and the other that traveled 130 kilometers in the same time? Record and bubble in your answer below. Show all work! Graphing Motion 6.8D In the graph to the right, how many kilometers has the object moved after 10 minutes? In the graph to the right, how many kilometers has the object moved after 20 minutes? In the graph to the right, how many minutes did it take for the object to move 3.5 kilometers? Which of the following situations could be represented by this graph? A. A boy walks 1.5 km to the park in 10 minutes. Then he walks backwards to his house in 10 minutes. Then he runs to his friend s house which is 2 km away in 20 minutes. B. A boy walks 10 kilometers to the park for 1.5 minutes. Then, he stops for a 10 minute rest. After that, he continues on 2 km, which takes him 20 minutes. C. A boy walks 1.5 km to the park in 10 minutes. He stops for a 10 minute rest before continuing onto the store which is 2 km away from the park. It takes him 20 minutes to get from the park to the store. D. A boy walks 1.5 km to the park in 5 minutes. He stops for a 5 minute rest before continuing onto the store which is 20 km away from the park. It takes him 40 minutes to get from the park to the store Science Teaching Junkie, Inc. 9

10 Which graph shows the fastest speed? Circle your answer. The graph below shows the speed of a car traveling north over a 16 second time period. Based on the information in the graph, it can be concluded that in the first 8 seconds, the car is - A. changing its direction. B. accelerating at a constant rate. C. climbing a steep incline. D. experiencing less and less friction. Energy Transformations 6.9C Identify each of the 7 different forms of energy represented below. Label them using the following terms: mechanical, chemical, thermal, electrical, light (or EM energy), sound, and nuclear Science Teaching Junkie, Inc. 10

11 states that energy cannot be created or destroyed, but only transformed into different forms. Complete the chart using these types of energy: mechanical, thermal, electrical, light, sound, chemical. Beginning Energy Type Type(s) of Energy Converted To Hair dryer Battery Operated Radio Glow stick Piano Plant going through photosynthesis Roller coaster Flashlight 2014 Science Teaching Junkie, Inc. 11