Newton's Laws Review

What is inertia?

• the force that opposes motion of an applied force in order to balance it

• the force between 2 objects that is equal and oppsite

• an object's tendency to maintain its state of motion because it resists changing its motion

• a change in an object's speed and/or direction by speeding up, slowing down, or changing direction

According to Newton’s first law of motion, an object in motion that is not acted on by any unbalanced forces such as will

• remain in motion.
• eventually come to a stop.
• change its momentum.
• accelerate.

What kind(s) of objects have inertia?

• all objects with mass
• only objects at rest
• only objects in motion
• only objects whose motion is being changed

You are throwing a ball to your friend across the room. Which ball will take more force to throw?

• They are the same size, so they will take the same force because their inertia is the same.

• The bowling ball has a greater mass and therefore more inertia, so it will take more force.

• The basketball has a smaller mass, so it will take more force to overcome its inertia.

Answer explanation

The larger the mass, the larger the force required to cause the same change in motion. It is harder to throw a bowling ball across the room than it is to throw a basketball. 

The law of inertia (Newton’s First Law) applies

• to both moving and nonmoving objects
• only to moving objects
• only to objects that are not moving

An astronaut in outer space away from gravitational or frictional forces throws a rock. The rock will...

• gradually slow to a stop

• continue moving in a straight line at constant speed

• progressively accelerate, getting faster and faster forever

A driver stops suddenly at a red light. He is thrown forward against the seatbelt. Why?

• A force pushes him forward when he stops.

• The force of the seatbelt pushes him backwards.

• A force pushes the whole car forward, including the driver.

• The force of the brakes stops the car, but the inertia of the driver keeps his body moving.

Answer explanation

Because the force of the brakes acts on the car but not the driver, the driver keeps moving forward because of inertia until the seatbelt stops him.

A car moves at a constant speed without changing direction. What HAS to be true about the forces on the car?

• A force is pushing the car in the direction it's moving.

• The forces on the car are not balanced.

• The forces on the car are at equilibrium since they are balanced.

• Forces push on the car in all directions.

Answer explanation

The car isn't changing speed or direction, so the forces have to be balanced!

The combination of all forces acting on an object is called __________

• Parallelogram Rule
• Net Force
• Vector Quantity
• All the Jedi's using their abilities together

Which of the following is an example of an unbalanced force?

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