1. P2 Calculations

2. What is the acceleration of the bike ? 500 N 100 N Mass = 200kg F = m x a 400 = 200 x a 400 = a 200 2m/s 2 = a

3. Calculate the maximum power of the hairdryer ? P= I x V V= 6.5 x 230 V = 1495 W Current in amps Fan only1.0 Fan and heater 14.4 Fan and both heaters6.5 Watt is the unit of power

4. An athlete of mass 65kg runs at 8.5m/s. How much KE does she have? Ek = ½ m x v 2 Ek = ½ x 65 x 8.5 2 Ek = 2348J

5. What is the acceleration of the car ? 50m/s 10 m/s Time = 4s a = v-u t a = (50 – 10 ) / 4 a = 10m/s 2

6. A charge of 200C flows in 2 minutes around a circuit. How much current is flowing? I= Q / t I= 200 / 120 I = 1.7 A Remember time must be in seconds.

7. How much energy is transferred when the potential difference of 120 V is across a bulb and the charge that has flowed through is is 2 C? E= V x Q E= 120 x 2 E = 240 J HT ONLY

8. What is the weight of the baby on Earth ? Mass = 6 kg W = m x g W = 6 x 10 W = 60N Remember weight depends on gravity your mass is always the same!

9. A spring stretches by 10cm when 5 N is attached. What is its spring constant ? F = k x e 5 = k x 10 5 = k 10 0.5 N/cm= k

10. An athlete of mass 65kg runs at 8.5m/s. How much momentum does she have? p = m x v p = 65 x 8.5 p = 552.5kgm/s Remember momentum is conserved in collisions.

11. A car brakes with a constant force of 500N over a distance of 25m.How much work is done ? W = F x d W = 500 x 25 W = 12,500J This is also the Kinetic energy lost by the car.

12. A footballer of mass 95kg jumps up 1.5 m. How much PE does he gain? Ep = m x g x h Ep = 95 x 10 x 1.5 Ep = 1425J This will be converted to KE when he falls.

13. It takes 50 seconds for an electric motor to lift the person up to the helicopter. And it uses 21600J in this time. What is the power of the motor? P = E / t P = 21600 / 50 P = 432 W

14. 2000J of work is done by a charge of 200C when flows through the bulb? How much voltage is across the bulb ? V= W / Q V= 2000 / 200 V = 10V

15. Calculate the voltage across the 8 ohm resistor ? V= I x R V= 0.5 x 8 V = 4V

16. Calculate the speed of the vehicle during AB ? v= gradient of line a= 100 / 3 a = 33.3 m/s

17. Calculate the acceleration of the vehicle ? a= gradient of line a= 12.5 / 5 a = 2.5 m/s 2

18. Calculate the distance the vehicle travels whilst it is accelerating ? d= area under graph d= ½ b x h d = ½ x 5 x 12.5 = 31.25 m

19. What will the final velocities of the objects be when they collide ? 5m/s Before A 1Kg B 4Kg 5Kg 0m/s After Momentum before = Momentum after (5 x 1) + ( 4 x 0) = 5v 5 = 5v, so v = 1m/s v

20. How much energy is transferred when the potential difference of 120 V is across a bulb and the charge that has flowed through is is 2 C? E= V x Q E= 120 x 2 E = 240 J HT ONLY