Grade 6 Physical Pretest

Transcription

1 Grade 6 Physical Pretest Select the best answer to each question. 1. Which of these is an example of the conversion of gravitational potential energy into kinetic energy? A. a person running on a level track B. an apple falling from a tree to the ground C. a windup spring making a toy car move across the floor D. a rubber band being stretched to twice its normal length 2. Water is one of Earth s greatest resources. Which has the greatest kinetic energy? A. water cooling in a freezer B. water in a swimming pool C. water flowing in a river D. water behind a dam 3. Which of the following is NOT an example of the Law of Conservation of Energy? A. A toy car slows down as it rolls uphill. B. A bicycle speeds up as it rolls downwill. C. Water gains speed as it falls down a waterfall. D. Two balls at different heights have different potential energy. 4. The graph below shows the distance a car traveled over 5 seconds while moving on a freeway.

2 What was the average speed of the car? A. 0 m/s B. 14 m/s C. 28 m/s D. 30 m/s 5. Felipe made a graph showing distance versus time. What did Felipe plot on his graph? A. force B. speed C. work done D. direction of motion 6. Keesha ran out of time and could not complete the lab on motion. However, she turned in the results she recorded before the class period ended. She included the graph below as part of her report.

3 Keesha correctly predicted how long it would take for the object to move 3 feet. What was Keesha s prediction? A. 10 seconds B. 9 seconds C. 8 seconds D. 7 seconds 7. Which of the following describes a contact force? A. Earth and the moon pull on each other B. an ball s weight makes it fall C. a magnet holds a picture to a refridgerator D. a table supports a book 8. Rena wrapped an iron nail in a piece of copper wire and connected the wire to a battery, as shown below.

4 Then she held the nail above a pile of metal shavings. What type of force caused the shavings to move toward the nail? A. friction B. gravity C. electrical force D. magnetic force 9. Forces can act on an object to transfer energy. Which of the following examples is NOT an example of a force causing a transfer of energy? A. A push causes a rolling marble traveling at a constant speed to speed up. B. A push causes a rolling marble traveling at a constant speed to slow down. C. A push causes a rolling marble traveling at a constant speed to change direction only. D. A push causes a rolling marble traveling at a constant speed to slide across the floor. 10. The following table lists the weights and volumes of several items. Object Mass (g) Volume (cm 3 ) bowling ball 3,600 5,400 golf ball soccer ball 450 5,400 tennis ball Which object has the greatest gravitational force acting on it on Earth? A. bowling ball B. golf ball C. soccer ball D. tennis ball 11. When astronauts went to the moon, they wore space suits that nearly doubled their weight. But videos show the astronauts bouncing easily across the moon s surface, as if their space suits weighed nothing at all. Which statement best explains why the astronauts were able to walk so lightly on the moon s surface? A. The moon does not exert a gravitational force. B. The moon s gravitational force is the same as Earth s gravitational force. C. The moon s gravitational force is weaker than Earth s gravitational force. D. The moon s gravitational force is stronger than Earth s gravitational force. 12. Cara set two balls of equal mass on the table 10 cm apart. What happens to the gravitational force the balls exert on each other if she increases the distance between the balls to 100 cm? A. The gravitational force increases. B. The gravitational force decreases. C. The gravitational force remains the same. D. Small objects do not exert gravitational forces. 13. The following picture shows forces acting on a sneaker. Suppose that the sneaker is moving toward the spring scale.

5 In which direction is the sum of all the forces (the net force) acting? A. The net force is acting in an upward direction. B. The net force is acting in a downward direction. C. The net force is acting to the left. D. The net force is acting to the right. 14. Sean places a plastic block in a beaker of water. The block floats. What conclusion can he draw about the force or forces being exerted on the block? A. The block floats because gravity has no effect on objects in the water. B. The net force on the block is greater than zero and in the upward direction. C. The net force on the block is greater than zero and in the downward direction. D. The only force being exerted on the block is the upward force exerted by the water. 15. The box shown below is being acted on by four forces. Three of the forces are shown. What should the magnitude of the fourth force be for the forces on the box to be balanced? A. 30 N B. 60 N C. 120 N D. 260 N

6 Grade 6 Physical Pretest Answer Section MULTIPLE CHOICE 1. ANS: B A is incorrect because running is a conversion of chemical potential energy into kinetic energy. B is correct because an apple falling from a tree is a conversion of gravitational potential energy into kinetic energy. C is incorrect because the elastic potential energy of the spring is converted into kinetic energy of the toy car as it moves. D is incorrect because stretching a rubber band is a conversion of kinetic energy into elastic potential energy. STA: SC.6.P ANS: C A is incorrect because water cooling has little to no movement. B is incorrect because water in a swimming pool does not move much. C is correct because the flowing water has kinetic energy. D is incorrect because water behind a dam is not moving. This is an example of potential energy. STA: SC.6.P ANS: D A is incorrect because it shows that the car s kinetic energy decreases as its potential energy increases. B is incorrect because it shows that the bicycle s kinetic energy increases as its potential energy decreases. C is incorrect because it shows that the water s kinetic energy increases as potential energy decreases. D is correct because it does not show how the total energy in a system is constant. STA: SC.6.P ANS: D A is incorrect because the car s speed is equal to the slope of the line, and the slope of the line is not zero. Only a horizontal line has a slope of zero. B is incorrect because the car s speed is equal to the slope of the line, and the slope is determined by dividing the distance traveled by the total time, yielding 28 m/s, not 14 m/s. C is correct because the car s speed is equal to the slope of the line, and the slope is determined by dividing the distance traveled (140 m) by the total time (5 s), yielding 28 m/s. D is incorrect because the car s speed is equal to the slope of the line, and the slope of the line is 28 m/s, not 30 m/s. STA: SC.6.P ANS: B A is incorrect because force depends on mass and acceleration rather than distance and time. B is correct because speed is calculated by dividing the distance traveled by the time it takes to travel that distance. C is incorrect because work depends on force and distance. D is incorrect because the graph included distance and time, which shows speed rather than the direction in which the object moved. STA: SC.6.P ANS: B

7 A is incorrect because the constant speed is 1 foot/3 seconds, or 3 feet/9 seconds. B is correct because the object is traveling at a constant speed of 1 foot/3 seconds. C is incorrect because the object takes 3 seconds to travel 1 foot. D is incorrect because the object is traveling at a constant speed of 1 foot/3 seconds, and taking 9 seconds to travel 3 feet. STA: SC.6.P ANS: D A is incorrect because the gravitational forces act at a distance. B is incorrect because the gravitational force (weight) acts at a distance, through air. C is incorrect because the magnetic force acts at a distance, through the picture. D is correct because the upward force from the table acts through direct contact with the book. STA: SC.6.P ANS: D A is incorrect because friction is a contact force exerted by one surface on another. B is incorrect because gravity would pull the shavings down. The shavings were pulled upward by the force exerted by the nail. C is incorrect because neither the shavings nor the nail are electrically charged. D is correct because the electric current flowing through the wire turned the nail into an electromagnet, generating a magnetic force that acted on the metal shavings. STA: SC.6.P ANS: C A is incorrect because the change in speed results in an increase in the kinetic energy of the marble. B is incorrect because the change iun speed results in a decrease in the kinetic energy of the marble. C is correct because the push causes a change in direction without a change in speed. D is incorrect because the push causes an increase in the amount of friction between the marble and the floor, so the amount of heat energy produced due to friction is increased. STA: SC.6.P ANS: A A is correct because the bowling ball has the most mass, and the more massive an object, the greater the gravitational force acting on it. B is incorrect because the golf ball and the tennis ball have the least mass, and mass determines gravitational force. C is incorrect because the soccer ball has a similar volume to that of the bowling ball, but it does not have more mass than the bowling ball, and mass determines gravitational force. D is incorrect because the golf ball and the tennis ball have the least mass, and mass determines gravitational force. STA: SC.6.P ANS: C A is incorrect because all objects exert a gravitational force on other objects. B is incorrect because the mass and diameter of the moon are much less than those of Earth, so it exerts less gravitational force on objects on its surface than Earth does. C is correct because the mass and diameter of the moon are much less than those of Earth, so it exerts less gravitational force on objects on its surface than Earth does. D is incorrect because the mass and diameter of Earth is larger than the moon s, so it exerts a greater gravitational force on objects on its surface than the moon does.

8 STA: SC.6.P ANS: B A is incorrect because gravitational force decreases as the distance between two objects increases. B is correct because gravitational force decreases as the distance between two objects increases. C is incorrect because gravitational force is proportional to the masses of the two objects and the distance between them. D is incorrect because all objects exert gravitational forces on each other. STA: SC.6.P ANS: D A is incorrect because the upward force is balanced by an equal and opposite downward force. B is incorrect because the downward force is balanced by an equal and opposite upward force. C is incorrect because the shoe is moving to the right, not the left. The direction of motion must be in the direction of the net force. D is correct because the net force is in the direction of motion, which is to the right. STA: SC.6.P ANS: B A is incorrect because gravity effects all objects on Earth. B is correct because the forces acting on the block are unbalanced, with the greatest amount of force pushing upward on the block. C is incorrect because if the net force was in the downward direction, the block would sink. D is incorrect because there is more than one force acting on the block. STA: SC.6.P ANS: B A is incorrect because 30 N is one-half the amount of force needed. Student most likely divided the amount of force being exerted on the opposite side of the box by 2. B is correct because for the force pair to be balanced, the forces on both sides of the box must have a magnitude of 60 N. C is incorrect because 120 N is double the amount of force needed. Student most likely multiplied the amount of force being exerted on the opposite side of the boxy by 2. D is incorrect because 260 is the net force that would be exerted on the box if all forces were acting on the box in the same direction. STA: SC.6.P.13.3