1. 2.6 Understanding Impulse and Impulsive Force
Force and Motion
2.6 Understanding Impulse and Impulsive Force

2. IMPULSE
Is defined as the product of a force, F acting on an object of mass, m for time ,t
Impulse = Force x Time
Impulse = Ft
Also can be define as the change of momentum
Impulse= mv – mu
Impulse ,Ft = mv – mu
Unit kgms-1 or Ns
Is a vector quantity

3. IMPULSIVE FORCE
Large force that acts over a short period of time during collision or explosion
Also can be define as the rate of the change of momentum in a collision or an explosion
Formula :
F = mv – mu t
Unit kgms-2 or N
Example involving impulsive force:
Football
Playing golf
Playing baseball
Playing tennis
Playing badminton

4. Example 1:

5. Solution

6. Example 2

7. Solution

8. INCREASING THE TIME IMPACT TO REDUCE THE IMPULSIVE FORCE

12. DECREASING THE TIME IMPACT TO INCREASE THE IMPULSIVE FORCE

16. Exercise 1
A boy hits a 0.50kg ball and sends it moving the opposite direction. Figure shows the magnitudes of its velocity before and after being hit respectively. The time of contact between the land and the ball is 0.05s.
15 ms-1
20 ms-1
Calculate :
The impulse applied to the ball.
The impulsive force exerted on the ball by the hands.

17. Exercise 2
A 300g ball is thrown horizontally towards a vertical wall at a velocity of 12ms-1. On impact, the ball bounces back horizontally at a velocity of 10ms-1. If the ball is in contact with the wall for 0.02s, find:
The impulse
The force exerted on the ball.

18. Exercise 3
Figure shows a 2kg wooden block initially at rest on a smooth surface. A force of 8N is applied on the wooden block.
If the force acts for 3s:
What is the impulse on the block
What is the velocity of the wooden block after 3s?
2 kg
8 N
u = 0 v
t = 0s t = 3s

19. Exercise 4
A tennis ball and a piece of mud with the same mass ( kg) and moving at 9ms-1 both strike a wall. The mud sticks to the wall while the ball rebounds at 6 ms-1. Find the impulse on each object.
9ms-1
Mud
Tennis ball
9ms-1
6 ms-1