PN HAZIAH BT AWANG LAH SAS 2007

2.6 ANALYSING IMPULSE AND IMPULSIVE FORCE

F = m ( v-u ) t F = mv –mu t Ft = mv-mu

CASE 1 : Increasing Momentum

» Impulsive force increase, time interval decrease. Serious injury or serious damage

If the change in momentum occurs over a short time, the force of impact is large.

CASE 2 : Decreasing Momentum

→ Impulsive force decrease, time interval increase ≈ we can minimize injury and damage

If the change in momentum occurs over in a long time, the force of impact is small.

TEACHER’S SIGNATURE : ………………………………….

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Previous Knowledge a = v- u t

F = ma

Common Misconception :Impulse equals momentum

The truth ;Impulse equals change in momentum

Impulse The change of momentum

F = impulsive force

The force of impact = impulsive force

TRY THIS !!!Tape some toothpicks to one side to one floppy disk box. Fire a dart from a dart gun against the smooth side of the box.The dart sticks and the box slides an observed distance across the tableThen repeat, with the box turned around so the dart hits the toothpick sideObserved the distance of the box.

PN HAZIAH BT AWANG LAH SAS 2007

HOW TO REDUCE IMPULSIVE FORCE

1. Physics in sportHigh Jump Tournament : Used mattres to increase time interval Therefore the impulsive force will decrease

2. Physics in safety features in vehicleSeat Belt : The time interval will increase when the collision occurred Therefore we can reduce the injury for the passenger

3. Give your own example

THE BENEFIT OF IMPULSIVE FORCE

1. Physics in our daily life

2. Give your example the benefit of impulsive force in sports.

SOLVING PROBLEM :

1. A ball of mass 400 g moving at a velocity of 16 ms-1 collides with vertical wall. It then bounces from the wall with the velocity of 9.0 ms-1. What is the magnitude of the impulse on the ball.

2. Syafiq kicked a stationary football with a force with 1100 N. The mass of the ball is 600 g and the time of contact between his feet and the ball is 9 x 10-3 s. At what speed will the ball start to move

3. A participant of a camping activity is involved in climbing a wall and jumping from the top of the wall. Before landing, the participant bent his legs. Why?

2.7 SAFETY FEATURES IN VEHICLE

Make a pamphlet about safety features in vehicles. In your pamphlet, must be included:

(i) Picture(ii) How it works to reduce the impulsive force (iii) How the features save the passenger from serious injury

TEACHER’S SIGNATURE : ………………………………….

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Pestle and mortar are made from stone.The spices is easily crushed because …………………

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