Impulse Physics Topic 6 Notes 2 1 of

(Impulse) Physics Topic 6 Notes 2 1 of 5 © Boardworks Ltd 2009

Force and change in momentum When a force is applied to an object, the object’s velocity changes. This means that its momentum will also change. The change in momentum depends on the size of the force and the time for which it is applied. The relationship between these values is shown by this equation: F = impulse (or Dp) Dt l Momentum is measured in kilogram meters per second (kg m/s). l Time is measured in seconds (s). l Force is measured in newtons (N). 2 of 5 © Boardworks Ltd 2009

Chart Measurement impulse 3 of 5 name Dp definition Ft (change in p) units SI kgm/s Tool __ © Boardworks Ltd 2009

It’s not the fall that kills, it’s the sudden stop at the end…. . • seat belts • air bags • bungee jumping • parachute 4 of 5 © Boardworks Ltd 2009

Change in momentum question 1 A soccer ball with a mass of 0. 5 kg is kicked from stationary to a velocity of 8 m/s. The 1 kicker’s foot is in contact with ball for 0. 1 seconds. What force does the kicker use? 2 m = 0. 5 kg 3 F= 4 5 Dp t 5 of 5 Dp = Ft = m. Dv = (0. 5 kg)(8 m/s) = 4 kgm/s 0. 1 s 6 vf = 8 m/s 0. 1 s = 40 N © Boardworks Ltd 2009

Change in momentum question 2 A tennis ball is rolled at a toy car with a mass of 0. 1 kg. The car is moved with a velocity of 0. 5 m/s. If the ball and car are in contact for 0. 05 seconds, with what force is the tennis ball rolled? 1 2 m = 0. 1 kg 3 F= 5 4 m. Dv Dt vf = 0. 5 m/s t = 0. 05 s Dp = Ft = m. Dv = (0. 1 kg x 0. 5 m/s) = 0. 05 kgm/s 0. 05 s 6 6 of 5 = 1 N © Boardworks Ltd 2009

Bouncing If a flower planter falls on your head, would it hurt less if it bounces or if it breaks? Breaking hurts less! Bouncing hurts more because you have need an impulse to stop it, then another impulse to make it bounce back up…… In movies, they make special window glass, bottles and furniture that are made to break easily!!!!! 7 of 5 © Boardworks Ltd 2009

Quiz Time 8 of 5 © Boardworks Ltd 2009