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Forces and Motion - Unit Review

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  • Object A has a mass of 20 kg. Object B has a mass of 50 kg. If they are both pushed with the same force, which will accelerate faster?
    Object A
  • You use a ping pong ball to knock your friends water bottle off their desk. The water bottle falls backward, but the ping pong ball also bounces back towards you. Why does this happen?
    Newton's 3rd Law: The ping pong ball exerted a force on the water bottle, but the water bottle exerted a force back on the ping pong ball, pushing it back.
  • TRUE or FALSE: When two objects with different masses collide, only the larger object exerts a force on the smaller one, causing it to move.
    FALSE - both objects exert equal and opposite forces on each other
  • An object has a mass of 10 kg and accelerates at 3 m/s2. How much force is being applied?
    30 N
  • TRUE or FALSE: One golf ball is moving and one is still. When they collide, both balls exert forces on each other in opposite directions, even though one isn't moving.
    TRUE
  • A frog jumps off of a lily pad, which is in the water, onto a rock. Which will move - the lily pad, the rock, or both, and in which direction?
    The lily pad will move away from the rock.
  • TRUE or FALSE: In a collision between A and B, increasing the mass of A will always increase the acceleration of B.
    FALSE: It will increase the FORCE between the two objects, but will not directly affect the acceleration. The acceleration in a collision is dependent on FORCE
  • Two unequal forces are exerted in opposite directions on an object. Will the object accelerate?
    Yes - the forces are unbalanced so the object will move in the direction of the stronger force.
  • When a meteor gets near the Earth, it curves toward the Earth. Why doesn't the Earth curve toward the meteor?
    Though they are both exerting equal gravitational forces on each other, the Earth is much more massive, and thus does not move.
  • What type of motion could line C represent - a bird landing in sand, a car accelerating away, a car coming to a sudden stop, or a horse slowing from a trot to a walk?
    a car accelerating away
  • What type of motion does line B represent - an object moving at a constant speed, and object at rest, or an object moving at an increasing speed?
    an object moving at a constant speed
  • Amber hikes 10 miles East then 5 miles West. The trip takes her 5 hours. What is her velocity?
    1 mile per hour East
  • Person A has a mass of 100 kg. Person B has a mass of 50 kg. What will happen when they collide?
    Both will exert equal and opposite forces on one another, but person B will bound backward more than person A because they have less mass.
  • Amber hikes 10 miles East then 5 miles West. The trip takes her 5 hours. What is her distance?
    15 miles
  • Amber hikes 10 miles East then 5 miles West. The trip takes her 5 hours. What is her displacement?
    5 miles East
  • Object A and B both have a mass of 50 kg. If object A accelerates slower than object B, on which object was more force applied?
    Object B
  • Name 2 examples of noncontact forces
    Possible answers: gravitational force, magnetic force, and/or electric force (among others)
  • If a hovercraft is moving with an acceleration of 6 m/s2 and a 52 kg person is onboard, how much force is being applied?
    312 N
  • FILL IN THE BLANK: If the forces on an object are ____, the object will not move.
    balanced
  • Why does a hockey puck move more easily on ice than cement?
    There is less friction on the ice because the surface is smoother.
  • You are riding in a car with your family. The car is going 50 km/hr. How fast are you moving relative to your family?
    0 km/hr - you are all traveling at the same speed, so compared to them, you are not moving
  • A hovercraft uses blowers to force air underneath it, allowing it to coast on a thin layer of air. What type of force is it reducing?
    Friction
  • TRUE or FALSE: When a baseball is hit by a baseball bat, they exert equal and opposite forces on one another, which cancel each other out for a net force of 0.
    FALSE: The forces are exerted on two different objects, so although there are equal and opposite forces applied, the effects do not cancel each other out.
  • What is the acceleration of a hovercraft if the mass of a person onboard is 68 kg and the amount of force acting on them is 408 N.
    6 m/s2
  • Alex is pushing on a box. Why doesn't the box move even though Alex is pushing on it?
    The force of friction is balancing the force of Alex's push.
  • What is the net force on the box in the picture?
    100 N to the right
  • A golfer uses his club to hit his ball across the green. Why does the ball accelerate away from the club more than the club moves away from the ball?
    The ball has less mass, so the same amount of force that is applied to both causes the ball to move farther.
  • Two equal forces are exerted in opposite directions on an object. Will the object accelerate?
    No - the forces are balanced.
  • Why is the front of a car designed to crumple during a crash?
    It increases the amount of time it takes for the crash to happen, which decreases the acceleration, which decreases the amount of force from the impact.
  • What is inertia?
    resistance to change in motion
  • Based on the pictures of spring scales shown here, which object (A, B, C, or D) has the least weight?
    A
  • Amber hikes 10 miles East then 5 miles West. The trip takes her 5 hours. What is her speed?
    3 miles per hour
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