Unit 4 Mastery Check

If the forces acting on an object are unbalanced, what must be true about the motion of this object?

• It must be at rest.

• It must be accelerating.

• It must be going the same direction.

• It must have the same force on each side.

A hot air balloon floats low in the sky. You see it pass your house and 30 seconds later pass a building you know to be 120m away. What is the estimated speed of the balloon?

Aaliyah claims that when someone sits down on a chair, they are exerting a force on the chair and that is all that happens. Her friend disagrees with her, citing Newton's Laws of Motion. Is Aaliyah correct? Why or why not?

• Aaliyah is correct because Newton's 1st Law of Motion states that if the chair exerted a force, then her motion would change.

• Aaliyah is correct because Newton's 3rd Law of Motion states that for every action there is an equal and opposite reaction and the chair does not show any action.

• Her friend is correct because Newton's 1st Law of Motion states that if the chair were to be exerting a force, then her motion would change.

• Her friend is correct because Newton's 3rd Law of Motion states that for every action there is an equal and opposite reaction and the chair's action counteracts the person's action, so that neither move.

A golf ball is balanced on a holder. The upward force from the holder balances the downward gravitational force on the ball and the ball is at rest. Jerry swings his club, applying force to the ball causing it to acclerate onto the field. Which of Newton's Laws does this correctly demonstrate?

• Newton's Universal Law of Gravitation

• Newton's First Law of Motion

• Newton's Second Law of Motion

• Newton's Third Law of Motion

To calculate how much work it takes to lift a shopping bag, besides the distance of the bag being lifted off the ground, what other information do you need to know?

• the shape of the bag

• the speed at which the bag is lifted

• the force being applied by the bag/person

• the distance the bag is being lifted off the ground

Donald is walking forward while carrying a backpack on his back. Which of the following statements is NOT TRUE?

• Work is is not being done because Donald is not directly picking up or putting down his backpack.

• Work is always being done on every object despite it's direction.

• Work is not being done on the backpack because the backpack's direction of force is down, while Hercules' direction of force is forward.

• Work is not being done on the backpack because Donald's motion is carrying him forward, not the backpack's.

. A student uses 86 N of force to push a box 12 m meters down the driveway. How much work did the student do to move the box?

Amal lifts a box with a force of 100 N and sets it on a tabletop 2 m high. Lexi pushes an identical box up a 5 m ramp from the floor to the top of the same table. Which student did the MOST work?

• Amal did the most work.

• Lexi did the most work.

• Amal and Lexi did the same amount of work.

• The mass of each student must be known to determine who did more work.

A machine has an output force of 60 N when an input force of 20 N is applied to it. What is the mechanical advantage of this machine?

• 3

• 300

• 0.03

• 1200

• You must use the formula for force and calculate the acceleration.

• You must use the formula for work and calcuate the distance

• You must use the formula for speed to calculate the distance each car traveled.

• You must calculate the input force so you can determine the output force for mechanical advantage.