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Colegio Real de Panamá

8th Grade Science: Forces and Motion

Write the letters of the correct answers on the lines at left. (1 point)

______ 1. Daylon’s family just bought a new puppy, and Daylon decided to take him for a walk. He put the puppy in a wagon and pulled the wagon along the sidewalk. From which of these reference points does the puppy appear to be moving?

A. Daylon

B. the wagon

C. the sidewalk

D. the puppy’s collar

______ 2. Two school classes are playing tug-of-war with a rope. One class pulls on the rope with a 75 N force to the left, while the other pulls with a 40 N force to the right. Which two statements describe this situation? (2 points)

A. The forces are balanced, and the rope does not move.

B. The forces are unbalanced, and the rope will move to the left.

C. The net force on the rope is 115 N to the right.

D. The net force on the rope is 35 N to the left.

______ 3. You might have noticed that a feather falls slowly toward the ground, while a ball falls rapidly. Which statement correctly explains the motion of these objects? (1 point)

A. The ball does not experience fluid friction as it falls.

B. Gravity is the only force acting on the feather and the ball.

C. The acceleration of the ball and feather are the same.

D. The feather experiences more fluid friction than the ball.

______ 4. Nicki rides her bike at a constant speed for 6 km. That part of her ride takes her 1 hour. She then rides her bike at a constant speed for another 9 km. That part of her trip takes her 2 hours. What is her average speed? (1 point)

A. 3.00 km/h

B. 5.00 km/h

C. 5.25 km/h

D. 7.50 km/h

Circle the words that correctly complete the paragraph. (2 points)

5. Susan ran a 400-m sprint at a track meet, and her final time was 65 s. She reported that her velocity in the race was 6.15 m/s. Susan’s statement was inaccurate because she mentioned only (direction / acceleration / slope / speed). She did not include (acceleration / speed / direction / slope), which is also a part of velocity.

Use the information below to answer questions 6 and 7.

Georgia loves to drop water balloons from her third-floor balcony into a dumpster located on the street below. Her brother filmed one balloon falling. He measured the height of the balcony rail. Then he used the video camera’s time feature to figure out how far the balloon had traveled from Georgia’s hand after each quarter of a second. He listed the times and distances in a table:

6. Using the data that Georgia’s brother collected, graph the distance the water balloon traveled over 1.5 seconds. (5 points)

Write an answer for the following question in the space provided.

7. Based on the graph, did the balloon travel at a constant speed or did it accelerate? Provide math-based evidence to support your claim. (5 points)

Write the letters of the correct answers on the lines at left.

______ 8. Connor received a new puppy as a birthday gift. The puppy’s food bowl was placed on a mat to keep spilled food off the floor, but every morning the food bowl is sitting across the room. Which statement accounts for this situation? (1 point)

A. According to Newton's first law, the bowl has inertia.

B. According to Newton's first law, the dog applied force to the bowl to move it.

C. According to Newton's second law, an action force was applied to the bowl.

D. According to Newton's third law, the bowl applied a reaction force to the puppy.

______ 9. Nikhil bought a large plant in a planter for his mother. He took it home and pushed it around his living room until he found a good location for it near a window. After he watered the plant, he was very surprised at how difficult it was to push the planter. Based on Newton’s second law, why does it become more difficult to move the planter? Choose the three statements that apply. (3 points)

A. With the water added, the planter had more mass and more inertia.

B. Nikhil had to apply more force to produce the same acceleration.

C. Increased inertia means that less force is needed to move the planter.

D. If Nikhil used the same amount of force, the acceleration of the moving planter would be less after adding the water.

Use the information below to answer questions 10 and 11.

Teresa did a trick in which she placed dishes on a tablecloth that was draped over a card table. She pulled quickly on the tablecloth, and it came off the table, leaving the dishes behind on the table. (3 points)

Circle the phrases that correctly complete the paragraph.

10. The inertia of the dishes kept them on the table, according to (all three of Newton’s laws / Newton’s first law / Newton’s second law / Newton’s third law). The tablecloth moved when she applied a force to it, as explained by (Newton’s first law / all three of Newton’s laws / Newton’s third law / Newton’s second law). When she pulled on the tablecloth with an action force, the tablecloth exerted a reaction force on her, as explained by (all three of Newton’s laws / Newton’s third law / Newton’s second law / Newton’s first law).

Write an answer for the following question in the space provided.

11. Teresa’s friend tried the same trick and ended up with a pile of broken dishes on the floor. Teresa told her that she didn’t pull the cloth quickly enough. She also said that her friend might have better results with heavier dishes. Using Newton’s laws, explain why these were good suggestions. (5 points)

Write the letters of the correct answers on the lines at left. (1point)

______ 12. Pam’s family is clearing some land, and there is a large boulder sitting on top of the ground. Even with the entire family pushing on it, they cannot move it. Which type of friction exists between the boulder and the ground?

A. fluid

B. rolling

C. sliding

D. static

______ 13. Do you believe that you are pulled towards your science book, a bunch of grapes in your lunch, and your school building because of universal gravitation? Which two statements about universal gravitation are true? (2 points)

A. Gravity acts between you and each of these objects because all have mass.

B. Gravity does not act between objects that are far apart, such as you and the sun.

C. Gravity only pulls things in a downward direction, such as toward Earth's surface.

D. Gravity acts between any two objects in the universe.

Circle the words that correctly complete the paragraph. (Assume the measurements are taken on Earth.) (3 points)

14. Pablo measured his horse at 1000 lbs, which is a measure of the horse’s (mass / acceleration / speed / weight). He also knows that the horse is 454 kg, which is a measure of the horse’s (speed / acceleration / mass / weight). Another measure of the horst is 4450 N, which is another way to state the horse’s (speed / acceleration / weight / mass).

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Name_________________________ Number: _____ Score: ___ / 35

Date: ____ /____/ 2020 Professor: Yiannis Gleglés

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