Momentum and Newton's Laws

Mrs. Lights explains Newton's Third Law of Motion and momentum, using examples like a hammer and nail, and a swimmer in water. She discusses momentum as mass times velocity, and compares the momentum of a golf ball and a bowling ball. The law of conservation of momentum is introduced, with examples of collisions and graphical analysis. Practical questions are posed to reinforce understanding.

What does Newton's Third Law of Motion state?

• The force of gravity acts between all masses.

• An object in motion stays in motion unless acted upon by an external force.

• For every action, there is an equal and opposite reaction.

• Energy cannot be created or destroyed.

In the example of a swimmer, what is the reaction force?

• The swimmer's body moving forward.

• The water pushing back on the swimmer's hand.

• The swimmer's hand pushing the water.

• The swimmer's feet kicking.

How is momentum calculated?

• Velocity divided by mass.

• Mass times velocity.

• Force times distance.

• Mass divided by velocity.

Which object has more momentum: a fast-moving golf ball or a slow-moving bowling ball?

• It depends on the direction of motion.

• The golf ball because it is faster.

• They have the same momentum.

• The bowling ball because it is heavier.

What does the law of conservation of momentum state?

• Momentum can be created or destroyed.

• Momentum is always increasing.

• The total momentum of a closed system remains constant.

• Momentum is only conserved in elastic collisions.

In a closed system, if one object's momentum decreases, what happens to another object's momentum?

• It remains the same.

• It becomes zero.

• It increases by the same amount.

• It also decreases.

After the collision of two train cars, what happens to the momentum of the system?

• It remains the same.

• It decreases.

• It becomes zero.

• It increases.

In the train car example, why does the green car move faster after the collision?

• It has more mass.

• It was pushed by an external force.

• It was initially moving faster.

• It gained momentum from the blue car.

At what time does the ball have zero momentum in the graphical analysis?

• At 3 seconds.

• At 0 seconds.

• At 2.5 seconds.

• At 1 second.

What is the speed of the ball after 1.25 seconds, given its momentum and mass?

• 13 meters per second.

• 10 meters per second.

• 5 meters per second.

• 15 meters per second.