Forces and Motion Review

The illustration shows people pushing farm carts of equal mass. Each person is pushing with an equal force (F) in the direction shown. How does the acceleration of Cart A compare to the acceleration of Cart B?

• It is twice the magnitude (amount of force), but in the opposite direction of cart B’s acceleration.

• It is twice the magnitude (amount of force) and in the same direction as cart B’s acceleration.

• It is the same magnitude (amount of force), but in the opposite direction of cart B’s acceleration.

• It is the same magnitude (amount of force) and in the same direction as cart B’s acceleration.

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A science teacher dropped a 5.0 kg brick (weight = 50 N) off of the roof of his house and into the swimming pool below. When making contact with the pool, the brick experienced an upward force of 20 N.

Which BEST predicts the motion of the brick once it makes contact with the pool?

• The brick will stop moving, because a force exerted by the water will cause the velocity to decrease.

• The brick will continue to accelerate, because the force of gravity is stronger than the upward force exerted by the water.

• The brick will continue moving at a lower velocity, because the force exerted by the water will cause the velocity to decrease.

• The brick will maintain a constant velocity, because the force of gravity is stronger than the upward force exerted by the water.

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Are the forces on the book balanced? Why or why not?

• Yes, because gravity is pulling the book down and the table is pushing the book up.

• Yes, because gravity is pulling the book up and gravity is pushing the book down.

• No, because the force of gravity and the table exert a different amount of force.

• No, because the force of gravity and the table are not of the same magnitude.

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NGSS.3-PS2-1

An elevator is supported by a cable and is moving downward through the elevator shaft at constant speed. How does the upward tension force in the cable compare to the downward force of gravity?

• The only force acting on the elevator is the force of gravity because it is moving downward.

• The upward tension force in the cable is greater than the downward force of gravity.

• There are no forces acting on the elevator because it is moving at constant velocity.

• The upward tension force in the cable is equal to the downward force of gravity.

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NGSS.MS-PS2-2

The force of 100 N is applied to the front a truck. Which of the following would balance the force and cause the truck to remain still?

• applying 100 N in the opposite direction because the forces are of equal magnitude and would balance each other out

• applying 100 N in the same direction because the forces are of equal magnitude and would balance each other out

• applying 50 N in the opposite direction because the forces are of differing magnitude and would balance each other out

• applying 50 N in the same direction because the forces are of differing magnitude and would balance each other out

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Which THREE examples BEST show when balanced forces are acting upon an object?

• a book laying on a table

• a fidget spinner spinning

• a car stopped at a red light

• a balloon floating up into the air

• a rope being pulled equally from opposite ends until it is tight

How will the box move?

• The box will not move.

• The box will move upward.

• The box will move to the left.

• The box will move to the right.

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If a ball is rolling with 5 pounds of force, how much force will be needed to stop the ball from rolling and why?

• It would take 25 pounds of force to stop the ball from rolling because it takes five times as much force to stop as object.

• It would take 2.5 pounds of force to stop the ball from rolling because it takes half of the amount of force to stop an object.

• It would take 10 pounds of force to stop the ball from rolling because it takes double the amount of force to stop an object.

• It would take 5 pounds of force to stop the ball from rolling because the same amount of force must be used to stop the object.

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The planets with the solar system all orbit the sun in elliptical paths at different orbital velocities (speeds). Which argument BEST explains why the planets orbit the Sun in the Solar System?

• The Sun has a strong gravitational field that keeps all the planets in a fixed orbital pattern around it.

• The planets have a strong gravitational field that keeps the Sun in a fixed orbital pattern around them.

• The Sun has a strong magnetic field, and the planets have a common electrical charge that keeps the planets in a fixed orbital pattern.

• The Sun has a strong magnetic field, and the planets have an opposite magnetic charge that keeps the planets in a fixed orbital pattern.

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Which is a result of the effect of gravity?

• Rocket engines can force objects into space.

• Air friction causes falling objects to slow down.

• Airplanes are able to fly without falling to the ground.

• Released objects always fall toward the center of the Earth

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