Newtons Laws Of Motion And Momentum

Question 1

Describe a perfectly elastic collision

Answer 1

When momentum and kinetic energy is conserved, and no energy is dissipated

Question 2

What happens in inelastic collisions?

Answer 2

Some of the kinetic energy is converted into other forms during the collision. However, momentum is always conserved.

Question 3

What are the units of impulse?

Answer 3

Ns

Question 4

State, Newton’s first law of motion

Answer 4

The velocity of an object will not change, unless a net force acts upon it

Question 5

State, Newton’s second law of motion in terms of momentum ( when mass is not constant) and give equation

Answer 5

The rate of change of momentum of the object is directly proportional to the net force which acts on the object
F= change in momentum/ change in time
And takes place in the direction of that force

Question 6

Why can you not use force equals mass times acceleration when the object is accelerating close to the speed of light

Answer 6

Because the mass of the object will change

Question 7

State Newton’s third law

Answer 7

If an object, A exerts a force on object, B then object B will exert an equal and opposite force on objectA

Question 8

How can we reduce the impact of the force without changing momentum or speed?

Answer 8

We can increase the time the impact takes

Question 9

What are crumple zones and what do they do?

Answer 9

Crumple zones are areas at the front and rear of a car that are designed to crumple on impact
They absorb some of the cars kinetic energy when they deform, which would otherwise be transferred to the passengers or the other object in the collision
They increase the time taken for the car to slow down. This intern reduces the forces acting on the passengers and whatever the car has hit.

Question 10

What are airbags and what do they do?

Answer 10

Airbags are cushions in the dashboard and elsewhere that inflate very quickly on collisions. This makes the passengers slow down gradually, therefore increasing the
And also stop passengers from hitting the dashboard et cetera

Question 11

How are seatbelts designed to protect passengers?

Answer 11

Seatbelts are designed to be stretched slightly, however, they still hold the passenger in place in the car, stopping them from being thrown from their seats. They absorb some of the passengers kinetic energy by stretching, and they increase the time for the passenger to come to a stop.

Question 12

A spacecraft travels through space and the engine is used to accelerate the spacecraft to a given velocity the engine is then switched off. the force of gravity acting on the spacecraft is negligible state, and explain the motion of the spacecraft after the engine is switched off

Answer 12

Space is a vacuum therefore, there is no resistant forces acting on the spacecraft. This means there is no net force. Therefore the spacecraft will continue to travel in the same direction at constant velocity.

Question 13

What is a spacecraft is travelling through space at constant velocity, the probe and the engine separate the probe objects, the engine backwards, describe and explain how the probes motion is affected by ejecting the engine

Answer 13

The engine exert a force onto the probe and the probe exerts an equal and opposite force onto the engine
Therefore, the probe will accelerate forward as the engine is ejected

Question 14

Before a probe hit the surface of a planet, it inflates airbags describe how these airbags reduce the damage sustained by the probe as it strikes the planets surface

Answer 14

The airbag increases the length of time over which the momentum changes during impact
Therefore, the maximum force experienced by the probe will decrease as changing momentum equals four times changing time .

Question 15

What is the area under a force time graph equal to?

Answer 15

It is equal to the impulse and therefore equal to the change in momentum

Question 16

When a tennis player hits a ball, they continue to swing their racket. After the initial moment of contact, explain how this motion can allow a player to hit a faster shot than if they were to stop their stroke immediately after the moment of contact.

Answer 16

The time of contact between the board and the racket increases and as imposter equals force times time the impulse will also increase as the contact time increases.
As impulse equals the change in momentum , the momentum will also increase, so the ball will leave the racket at a greater speed as momentum is proportional to speed

Question 17

Name the object that experiences a force of magnitude W, but in the opposite direction to W

Answer 17

Earth

Question 18

According to a student, the normal contact force will equal the weight of an object when the object is stationary state why this is incorrect

Answer 18

Because the forces are not the same type

Question 19

Give the two equations for impulse

Answer 19

Impulse= Mv
Impulse= rate of change of momentum

Question 20

How do we find the change in velocity or momentum?

Answer 20

Final minus initial

Question 21

Object an object collide using newtons third law of motion explain the relationship between impulse experienced by A and the impulse experience by B during the collision

Answer 21

A will exert an equal opposite force onto B vice versa therefore the impulse experience by a is equal opposite to the impulse experience by B however the time of contact is equal for both a and B as impulse equals the rate of change of momentum

Question 22

States of principle of conservation of linear momentum

Answer 22

Total momentum is conserved for a closed system

Question 23

Explain what is meant by an inelastic collision

Answer 23

There is some loss of kinetic energy during the collision