Module 3.5 - Momentum and Impulse ✓

Question 1

What is equation for le momentum?

Answer 1

p = mv

Question 2

State the law of conservation of momentum?

Answer 2

The total momentum before collision is equal to the total momentum after the collision in a closed system

Question 3

What is a ‘perfectly elastic’ collision?

Answer 3

A perfectly elastic collision is one where momentum and kinetic energy is conserved. An inelastic collision has some kinetic energy converted to other forms during the collision (momentum is still conserved).

Question 4

Define momentum?

Answer 4

Momentum - a measure of how difficult it is to stop a moving object

Question 5

State Newton’s second law

Answer 5

The resultant force, F exerted on a body is directly proportional to the rate of change of linear momentum, p, of that body

Question 6

State Newton’s first law

Answer 6

An object at rest will stay at rest, and an object in motion stay in motion with the same velocity, unless acted upon by an unbalanced net force

Question 7

How do you get the impulse equation (I = Ft)?

Answer 7

By rearranging the equation obtained from Newton’s second law: F = p/t
> p = Ft

Question 8

How do you get F=ma?

Answer 8

1) Newton’s 2nd law states that the force applied to a body, F is directly proportional to the rate of change of linear momentum
2) so F = k(p/t)
3) F = k(m(v-u)/t)
4) F = k(m((v-u)/t))
5) F = kma
5) Experimentally, k = 1

Question 9

State Newton’s third law

Answer 9

If an object A exerts a force on object B, then object B exerts an equal but opposite force on object A

Question 10

How is newton’s third law and conservation of momentum related?

Answer 10

A net force acting on an object means there is a change in acceleration (F = ma) so a change in momentum. However momentum must be conserved so the second object must exert an equal-sized force on the first.

Question 11

What is the basis of all car crash safety systems?

Answer 11

All car crash safety systems aim to increase the time that the force of the impact acts for. As the change in momentum remains the same, this reduces the force acting on people in the car.

Question 12

Name 3 safety features of cars?

Answer 12

• Air bags
• Large crumple zones
• Seat Belts

Question 13

How do crumple zones protect the passengers in a car?

Answer 13

• They absorb some of the car’s kinetic energy which would otherwise be transferred to the passengers
• They increase the time taken for the car to slow down, reducing the force

Question 14

How do seat belts protect wearers in a crash?

Answer 14

Seat Belts stretch slightly to:

• Absorb some of the wearer’s KE
• Increase the time taken for the wearer to come to a stop
• Hold the wearer in place in the seat