Force and Motion 2 6 Understanding Impulse and

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Force and Motion 2. 6 Understanding Impulse and Impulsive Force

Force and Motion 2. 6 Understanding Impulse and Impulsive Force

IMPULSE • Is defined as the product of a force, F acting on an

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

IMPULSIVE FORCE • Large force that acts over a short period of time during

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

Example 1:

Example 1:

Solution

Solution

Example 2

Example 2

Solution

Solution

INCREASING THE TIME IMPACT TO REDUCE THE IMPULSIVE FORCE

INCREASING THE TIME IMPACT TO REDUCE THE IMPULSIVE FORCE

DECREASING THE TIME IMPACT TO INCREASE THE IMPULSIVE FORCE

DECREASING THE TIME IMPACT TO INCREASE THE IMPULSIVE FORCE

Exercise 1 • A boy hits a 0. 50 kg ball and sends it

Exercise 1 • A boy hits a 0. 50 kg 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 the ball is 0. 05 s. 15 ms-1 20 ms-1 Calculate : 1. The impulse applied to the ball. 2. The impulsive force exerted on the ball by the hands.

Exercise 2 • A 300 g ball is thrown horizontally towards a vertical wall

Exercise 2 • A 300 g ball is thrown horizontally towards a vertical wall at a velocity of 12 ms-1. On impact, the ball bounces back horizontally at a velocity of 10 ms-1. If the ball is in contact with the wall for 0. 02 s, find: a) The impulse b) The force exerted on the ball.

Exercise 3 • Figure shows a 2 kg wooden block initially at rest on

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

Exercise 4 • A tennis ball and a piece of mud with the same

Exercise 4 • A tennis ball and a piece of mud with the same mass ( 0. 060 kg) and moving at 9 ms-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. 9 ms-1 Mud 9 ms-1 Tennis ball 6 ms-1