1. Twenty Questions Dynamics

2. Twenty Questions 12345 678910 1112131415 1617181920

3. 1. What is the unbalanced force? 15N – 7N 8N right 15N 7N

4. 2. What force always acts in the opposite direction to motion? Friction.

5. 3. Complete the table. PlanetGravity (N/kg) Mass of object (kg) Weight of object (N) Earth10 Mars4 9.8 10 98 40

6. 4. Why does ½ mv 2 = mgh? Energy is always conserved.

7. 5. What is Kinetic energy? The energy an object possesses due to it’s motion.

8. The work done against gravity in raising an object. 6.What is Gravitational potential energy?

9. 7. What formula denotes Electrical power? P = E/t

10. 8. What are the units of energy? Joules.

11. 9. Calculate the acceleration of the rocket as it takes off. F un =ma a =F un /m a =(21000000-7000000) (7000000/9.8) a = 19.6ms -2 7000kN 21000kN

12. 10. A ball rolls off a cliff, travelling at 3m/s. It hits the water below 5s later. 3m/s What is it’s final horizontal speed?

13. 11. A ball rolls off a cliff, travelling at 3m/s. It hits the water below 5s later. d = vt d = 3 x 5 d = 15m How far does the ball land from the base of the cliff?

14. 12. Give one situation in which friction is increased. i) applying the brakes of a car. ii) opening a parachute. iii) wearing rubber soled shoes for rock climbing.

15. 13. A ball rolls off a cliff, travelling at 3m/s. It hits the water below 5s later. v = u +at v = 0 + 9.8(5) v = 49ms -1 What is it’s final vertical velocity?

16. 14. What is Newton’s first law of motion? When balanced forces (or no forces at all) act on an object it remains at rest or continue to move at a steady speed in a straight line unless acted upon by an unbalanced force.

17. 15. A 100kg man takes 10s to accelerate to 20m/s from rest. What force does he exert to do this? F = ma = 100(2) = 200N a =(v-u) = (20-0) = 2ms -2 t 10

18. 16. What is Newton’s second law of motion? F un = ma

19. 17. A tram takes 25s to gain 10kJ of Potential energy. How powerful is the tram’s motor? E =Pt P = E/t P = 10000/25 P = 400W

20. 18. Give one situation in which friction is decreased. i) making racing cars streamlined. ii) oiling moving parts in a car engine. iii) using an air cushion on an ‘air hockey’ table.

21. 19. State the principle of conservation of energy. During any energy transformation the total amount of energy remains the same.

22. 20. What does the formula Ew = Fd represent? The work done in moving an object.