FORCES+CHANGE+MOMENTUM

IGCSE PHYSICS > FORCES AND MOTION > FORCES, MOVEMENT AND SHAPE

 * ~ 1 FORCES ||~ 2 ELECTRICITY ||~ 3 WAVES ||~ 4 ENERGY ||~ 5 SLG ||~ 6 MAGNETISM ||~ 7 RADIOACTIVITY ||

Definition Types Vectors || FORCES CAUSE MOVEMENT Friction F=ma Terminal velocity || FORCES CHANGE MOMENTUM Momentum Car safety Newton's 3rd law || FORCES CAUSE TURNING Moments Centre of Gravity Beam on trestles || FORCES CHANGE SHAPES Stretching ||
 * JUST FORCES

FORCES CHANGE MOMENTUM
1.18 recall and use the relationship between momentum, mass and velocity:

1.19 use the ideas of momentum to explain safety features. 1.20 use the conservation of momentum to calculate the mass, velocity or momentum of objects.

**EXAMPLES**

1 A skater of mass 50 kg travelling at 5 m/s collides with a skater of mass 40 kg travelling at velocity 2 m/s in the same direction. They cling together. With what velocity do they both move?



2 The same situation as #1 but the smaller skater is moving towards the big one. They cling together. What is their velocity after the crash?

3 A skater of mass 40 kg is stationary and throws a rock of mass 15 kg. He recoils with velocity 0.5 m/s. What was the velocity of the rock?

1.21 use the relationship between force, change in momentum and time taken:

EXAMPLE: A skater of mass 55 kg accelerates from 1 m/s to 5 m/s in 2 s. What is the forward force on her?

**EXPLAIN WHY:** You bend your legs when you jump from a height Egg boxes are made of soft card Crash helmets protect the head Air bags save lives Boxing gloves prevent cuts

1.22 understand Newton’s third law ACTIVITY: COPY THE TABLE AND COMPLETE THE THIRD LAW PAIRS
 * ** FORCE ON BODY B BY BODY A ** || **FORCE ON BODY A BY BODY B** ||
 * Pull of the earth on a person || Pull of the person on the earth ||
 * Push of the ground on your seat ||  ||
 * Push of car wheel back on the road ||  ||
 * Pull of the moon on the earth ||  ||
 * Push of a swimmer on the water ||  ||
 * Push of a rocket on the exhaust gases ||  ||
 * Pull of a magnet on a pin ||  ||
 * Push of racket on tennis ball ||  ||