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

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

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

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

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

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

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

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

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

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

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

All of the potential energy is converted to kinetic. 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?   answer 100J. All of the potential energy is converted to kinetic.  

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

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

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

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

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

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

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

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

20. A ball is kicked off a roof with a horizontal speed of 7ms-1 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? answer d = v x t d = 7 x 2 d = 14m  

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

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