Motion and Machines Quiz

the change of an object's position

• motion

• rest

• speed

• acceleration

Answer explanation

The change of an object's position is defined as motion. It refers to the movement of an object from one place to another, distinguishing it from rest, speed, and acceleration, which describe different aspects of movement.

A. Write the correct term. 2. a force that keeps objects from moving against other objects

• friction

• gravity

• magnetism

• inertia

Answer explanation

The correct term is 'friction' because it is the force that opposes the motion of objects sliding against each other, preventing them from moving freely.

determined by the mass and velocity of an object

• momentum

• energy

• force

• acceleration

Answer explanation

Momentum is defined as the product of an object's mass and its velocity. Therefore, the correct answer is momentum, as it directly relates to both mass and velocity.

the speed of a moving object in a given direction

• velocity

• speed

• acceleration

• momentum

Answer explanation

The speed of a moving object in a given direction is defined as velocity. Unlike speed, which only measures how fast an object is moving, velocity includes the direction of the movement.

occurs whenever an object speeds up, slows down, or changes direction

• acceleration

• velocity

• momentum

• force

Answer explanation

Acceleration occurs when an object speeds up, slows down, or changes direction. It is the rate of change of velocity, making it the correct choice among the options provided.

First Law of Motion

• A. Force is equal to the mass of an object and its acceleration.

• B. When one object exerts a force on another object, the second object reacts by exerting an equal force back on the first object.

• C. An object at rest tends to stay at rest, and an object in motion tends to stay in motion with the same direction and speed.

Answer explanation

Choice C correctly states the First Law of Motion, which describes the tendency of objects to maintain their state of rest or uniform motion unless acted upon by an external force.

Second Law of Motion

• Force is equal to the mass of an object and its acceleration.

• When one object exerts a force on another object, the second object reacts by exerting an equal force back on the first object.

• An object at rest tends to stay at rest, and an object in motion tends to stay in motion with the same direction and speed.

Answer explanation

The correct choice states that force equals mass times acceleration, which is Newton's Second Law of Motion. The other options describe different laws: action-reaction and inertia, respectively.

Third Law of Motion

• A. Force is equal to the mass of an object and its acceleration.

• B. When one object exerts a force on another object, the second object reacts by exerting an equal force back on the first object.

• C. An object at rest tends to stay at rest, and an object in motion tends to stay in motion with the same direction and speed.

Answer explanation

Choice B correctly describes Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. This means when one object applies a force, the other object exerts an equal force back.

Ruth likes to play softball and go bowling. She uses less force to throw a softball than she uses when she rolls a bowling ball.

• Force is equal to the mass of an object and its acceleration.

• When one object exerts a force on another object, the second object reacts by exerting an equal force back on the first object.

• An object at rest tends to stay at rest, and an object in motion tends to stay in motion with the same direction and speed.

Answer explanation

Ruth uses less force to throw a softball because it has less mass compared to a bowling ball. According to Newton's second law, force equals mass times acceleration, explaining her different force usage.

Dad slammed on the brakes when a ball bounced out in front of our car. My sister's doll that had been on the back seat ended up on the floor.

• Force is equal to the mass of an object and its acceleration.

• When one object exerts a force on another object, the second object reacts by exerting an equal force back on the first object.

• An object at rest tends to stay at rest, and an object in motion tends to stay in motion with the same direction and speed.

Answer explanation

When Dad slammed the brakes, the car exerted a force, causing the doll to move forward due to inertia. This illustrates Newton's third law: the doll reacted to the force by moving, demonstrating equal and opposite reactions.