UNIVERSITI KUALA LUMPUR MALAYSIAN INSTITUTE OF AVIATION TECHNOLOGY

Physics & AerodynamicsAAB 20103Impulse & Momentum

Lecturer’s Name: Madam Sharifah Fathin Adlina Binti Syed AbdullahGroup: 1BME1Student’s Name: 1. Adib Bin Lokman 532111141572. Ahmad Anas Zakwan Bin Zainal Azim 532111140753. Aida Hanani Binti Aziza 532111143354. Nabila Huda Binti Zakaria 532111143665. Nik Zarith Safiah Binti Nik Yusoff 53211114333

IMPULSE AND IMPULSIVE FORCE

Impulse is defined as the product of the force (F) acting on an object and the time of action (t).

Impulse exerted on an object is equal to the momentum change of the object.

Impulse is a vector quantity.

FORMULA OF IMPULSE

The SI unit of impulse is kg m s⁻1 or N s ⁻1.

Impulse Problem

An object has a mass of 1.16 kg and changes velocity by 23.46 m/s in 15.88 s. How large of a force acted on the object?

Answer: 1.71 N

IMPULSIVE FORCE

Impulsive force is the rate of change of momentum.

It is a force which acts on an object for a very short interval during a collision or explosion

Impulsive force = Impulse / time

The SI unit of impulse is kg m s⁻² or N.

The Effect of Time on an impulsive Force

1. From the formula for impulsive force, we get :

F = (mv - mu) / t

This shows that the time of action is very important factor in the calculation of the impulsive force.

2.When the time of action is prolonged, the impulsive force will decrease.

3. On the other hand, if the time of action is shortened, the impulsive force will increase.

High jump

During a high jump, a high jumper will land on a thick, soft mattress after the jump.

This is to increase the reaction time and hence reduces the impulsive force acting on the high jumper.

Safety Vehicles

Crumble Zone

The crumple zone increases the reaction time of collision during an accident.

This causes the impulsive force to be reduced and hence reduces the risk of injuries.

Airbag

The inflated airbag during an accident acts as a cushion to lessen the impact when the driver flings forward hitting the steering wheel or dashboard.

Other in safety vehicles feature

Seat belt Head rest Windscreen Padded dashboard Bumper Anti-Locking Bracking system (ABS)

example

A car of mass 500kg is traveling with a velocity of 25 m/s. The car hits a tree and is stopped in 0.05 seconds. What is the impulsive force acting on the car during the crash?

answer

m = 500kgu = 25 m/sv = 0t = 0.05 s

F=mv−mu/tF=(500)(0)−(500)(25)/0.05F= - 250,000 N

CONSERVATION OF MOMENTUM

The law of conservation of momentum: States that the total momentum o

system is conserved in a collision if no external forces acting on it.

The system is meant by a set of objects that interact with each other. An isolated

system is one in which the only forces present are those between the objects of the system.

Newton’s Cradles

Example

Question 2

A 2.3 g bullet moving vertically at 200 ms-1 hits a 2.0 kg wooden block which is resting on a horizontal platform as shown below.

After the impact , the bullet emerges with a speed of 30 ms-1. Determine the maximum height the block can reach upwards from its initial position.

Wooden block

platform

bullet

COLLISION THEORY

Is defined as an isolated event in which two or more bodies (the colliding bodies) exert relatively strong forces on each other for a relatively short time.

Two types of collisions : Elastic collision Inelastic (non-elastic) collision

ELASTIC COLLISION

Is defined as one in which the total kinetic energy (as well as total momentum) of the system is the same before and after total momentum) the collision.

Cases

List of formula

1

2

3

4

Conservation of

kinetic energy

Conservation of

momentum

Conservation of

momentum

Velocities After

Collision

ELASTIC PROBLEM 1:

Two objects, initially at rest, are driven apart by a spring. The one on the left moves away with a velocity of -2.44 m/s. The one on the right moves away with a velocity of 5.37 m/s. The one on the left has a mass of 14.31 kg. What is the mass of the one on the right?

6.50 kg

ELASTIC PROBLEM 2 :

 An object of mass , moving with velocity , collides head-on with a stationary object whose mass is . Given that the collision is elastic, what are the final velocities of the two objects. Neglect friction.

V1f = -6 m/s

V2f = 6 m/s

INELASTIC COLLISION

is defined as one in which the total kinetic energy of the system is not the same before and after the collision (eventhough the total momentum of the system is conserved)

Total momentum is

always conserved.

Kinetic energy is not conserved in inelastic collisions.

In a completely inelastic collisions, the object stick together after impact.

Basic inelastic collision

THANK YOU