EDEXCEL AS PHYSICS TOPIC 1: MECHANICS

SUB-TOPIC: UNITS, KINEMATICS & FORCES

1. a) With the aid of an example, explain the statement “The magnitude of a physical quantity is

written as the product of a number and a unit”. (2)

b) Explain why an equation must be homogeneous with respect to the units if it is to be correct.

(1)

c) Write down an equation which is homogeneous, but still incorrect. (2)

2. a) The list gives some quantities and units. Underline those which are base quantities of the

International (SI) System of units.

Coulomb, force, length, mole, newton, temperature interval

(2)

b) Explain the difference between scalar and vector quantities.

(1)

3.

4.

(4)

5. a) The joule is the SI unit of energy. Express the joule in the base units of the SI system. (1)

b)

(3)

c) Why might the formula still be incorrect? (1)

6.

(b) (i) The table is 0.70 m high. Show that the coin takes approximately 0.4 s to reach

the floor. (3)

(ii)Hence calculate the horizontal distance the coin travels in the time it takes to fall

to the floor. (2)

(c) A coin of greater mass is flicked with the same horizontal speed of 1.5 m s–1.

Compare the path of this coin with that of the coin in the first part of the question.

Explain your answer. You may be awarded a mark for the clarity of your answer. (4)

7.

(a) What does the time interval of 0.8 s at the beginning of the graph represent? (1)

(b) (i) How long does it take, from the instant the lights change to green, for the car to

reach the same velocity as the cyclist? (1)

(ii) Determine the distance between the cyclist and the car at this time. (3)

(c) What is the relationship between the average velocity of the cyclist and the average

velocity of the car for the time interval covered by the graph? (1)

8. (a) State the difference between distance and displacement. (1)

(b) Figure shows an idealised displacement-time graph for the journey of a train along

a straight horizontal track, from the moment when it passes a point A on the track.

Initially the train moves in an easterly direction away from A.

(i) Describe the position of the train relative to A at the end of the 8 minutes covered

by the graph. (2)

(ii) Plot a velocity against time graph of the journey shown in the figure above. (4)

*9. When asked to run one complete lap around a track, a student says, “However fast I

run, my average velocity for the lap will be zero”.

Comment on his statement. (3)

10. A ball is thrown from the top of a building toward a tall building 50m away. The initial

velocity of the ball is 20m/s – 40 degrees above the horizontal. How far above or below it’s

original level will the ball strike the opposite wall? (4)

11. (a) What is meant by Newton’s first law of motion? (2)

(b) Newton’s third law identifies pairs of forces.

(i) State two ways in which the forces in a pair are identical. (2)

(ii) State two ways in which the forces in a pair differ. (2)

12. A student is asked to provide an explanation of why a bottle on a table remains

stationary.

(a) Draw a complete free-body force diagram for the bottle. (2)

(b)

The student’s explanation contains errors. Rewrite the student’s explanation correctly. (3)

13. The Saturn V rocket used in NASA’s space programme had a mass of 3.04 × 106 kg.

It took off vertically with a thrust force of 3.40 × 107N.

(a) Show that the resultant force on the rocket is about 4 × 106 N. (3)

(b) Calculate the initial acceleration. (2)

(c) After 150 s the rocket reached a speed of 2390 m s–1. Calculate its average acceleration.

(d) Suggest why the initial acceleration and average acceleration are different. (1)

14. A 200N Wagon is to be pulled up a 30 degree incline at constant speed. How large a force

parallel to the incline is needed if friction effects are negligible (the incline surface is smooth)?

(3)

15. A 20kg box sits on a 30 degree incline. The coefficient of kinetic friction between the box

and incline is 0.30. Find the acceleration of the box down the incline. (4)

*16. In the fifteenth century, an explanation of projectile motion went as follows:

When you throw an object you give it a force called impetus. It moves in a straight line

until the impetus is used up. Then the object falls vertically to the ground.

The diagram shows the path described.

(a) Correct the diagram to show the path followed by a projectile according to modern

observations. Assume it has the same initial direction. (1)

(b) Explain why a projectile follows the path you have drawn. Your answer should

include reference to horizontal velocity. (3)

*17. You are asked to determine the acceleration of free fall at the surface of the Earth, g,

using a free fall method in the laboratory.

(a) Describe the apparatus you would use, the measurements you would take and explain

how you would use them to determine g. (6)

(b) Give one precaution you would take to ensure the accuracy of your measurements. (1)