Momentum

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Malaysia SPM Form 4, Chapter 2: Force and Motion
Back to Main Content.

1 Mind Map
2 What is momentum?
3 Principle of Conservation of Momentum
4 Explosion
5 Content 4
6 Content 5
7 Frequenly Asked Question
8 Additional notes
9 External Links

[edit] Mind Map

[edit] What is momentum?

Definition
Momentum is defined as the product of mass and velocity.

Momentum = mass × velocity

In equation, write this as:

p = m × v

Unit
The SI unit of momentum is kgms^-1.

Scalar or Vector?
Momentum is a vector quantity. The direction of momentum is same as the direction of velocity.

Example 1

An object of mass 6kg is moving with velocity 5ms^-1. What is the momentum of the object?

Answer
Mass, m = 6kg
Velocity, v = 5ms^-1

Momentum,

p = m × v = (6) x (5) = 30kgms^-1

Example 2

A car moves 200m in 4s. Given that the mass of the toy car is 600kg. Find the momentum of the car.

Answer
Mass, m = 600kg
Velocity, $v = {s \over t} = {{200} \over 4} = 50ms^{ - 1}$

Momentum,

p = m × v = (600) x (50) = 30,000kgms^-1

Momentum Change

Change of Momentum

= Final Momentum - Initial Momentum

= mv - mu

m = mass

u = initial velocity

v = final velocity

Example 3

A ball of mass 0.5 kg hits a wall with a velocity of 10 ms^-1 and bounces back with a velocity of 5 msms^-1. Calculate the change of momentum of the ball.

Answer

m = 0.5kg

u = 10 ms^-1

v = -10 ms^-1 [Take notes that when the ball move in opposite direction, the velocity become negative.]

Momentum Change,

= mv - mu

= (0.5)(-10) - (0.5)(10)

= -10kgms^-1

[edit] Principle of Conservation of Momentum

The principle of conservation of momentum states that in a system make out of objects that react (collide or explode), the total momentum is conserve if no external force is acted upon the system.

Momentum Before Reaction = Momentum After Reaction

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂