S4 Physics Forces 2

1. S4 Physics Forces 2 1 2 3 4 5 6 7 10 11 12 13 14 8 9 15 16 17 18 19 20 21 22

2. answer 1. State 3 possible effects of a force Change an objects Shape Speed Direction

3. answer .2.Define the gravitational field strength of a planet. The force of gravity acting on a mass of one kilogram.

4. answer 3. Write down a relationship between weight, gravitational field strength and mass. Weight = mass x gravitational field strength

5. answer 4. An object is travelling at 2ms-1 when the forces on it become balanced.Describe how the object now moves. The object continues to move in a straight line with a constant speed of 2ms-1

6. answer 5. An object of mass of 2kg has an acceleration of 3 ms-2.What unbalanced force is acting on the object? F = ma F= 2 x 3 F = 6N

7. answer 6. A person transfers 50J of energy when pushing an object 2m along a bench.What was the force exerted? EW = F x d 50 = F x 2 F = 25N

8. answer 7. A machine transfers 800J of energy in a time of 40 seconds.Find the power output. P = E/t P = 800/40 P = 20W

9. answer 8. State the equations which allow us to calculate kinetic and potential energy. Potential Energy EP = mgh Kinetic Energy EK = ½ mv2

10. answer 9. How much potential energy does a 5kg mass gain when it is lifted through 2m? EP = mgh EP = 5 x 9.8 x 2 EP = 98J

11. answer 10. An object of mass 3kg has a speed of 2ms-1. Calculate its kinetic energy. • EK = ½ mv2 • EK = ½ x 3 x 22 • EK = 6J

12. answer 11. An object gains 100J of potential energy when it is lifted from the ground. It is then dropped.Assuming no air resistance, what will be its kinetic energy when it hits the ground? 100J. All of the potential energy is converted to kinetic.

13. answer 12. State the difference between scalars and vectors A scalar has magnitude (size) only but a vector has magnitude and direction.

14. answer 13. Divide the following quantities into scalars and vectors.Force, mass, time, weight, velocity, energy, speed, displacement SCALARS mass, time, energy, speed VECTORS force, weight, velocity, displacement

15. answer 14. An object falls freely towards the earth. What is its acceleration? 9.8ms-2

16. answer 15. When a rocket lifts off it pushes hot gases downwards. Why does the rocket move up? The hot gases exert an upward force on the rocket. ( Newton’s 3rd Law)

17. answer 16. A model rocket has a weight of 2N. It produces a thrust of 8N. What is the unbalanced force acting on the rocket? 6N

18. answer 17. Why does a projectile follow a curved path? A projectile has both a horizontal and vertical motion. It moves across and down at the same time.

19. answer 18. Describe the horizontal and vertical motions of a projectile. HORIZONTAL constant speed VERTICAL constant acceleration( 9.8ms-2 )

20. answer 19. A ball is fired from a platform. State two ways of increasing the horizontal range. Increase the height of the platform. Increase the horizontal speed of the cannonball.

21. answer 20. A ball is kicked off a roof with a horizontal speed of 7ms-1 It hits the ground 2seconds later. How far from the is the roof when it lands? d = v x t d = 7 x 2 d = 14m

22. answer 21. An object is dropped from a tall building and hits the ground 3 seconds later. Find its speed on hitting the ground. a = (v-u)/t 9.8 = (v-0)/3 v = 29.4 ms-2

23. answer 22. How long does a geostationary satellite take to make one orbit of the earth? 24 hours