EX 1

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Ex 1 - Answer all questions

1. Fig. 1.1 shows a free-fall parachutist falling vertically downwards. The graph shows how the

speed of the parachutist varies with time

a) (i) State the name of the downward force acting on the parachutist.

(ii) State the name of one upward force acting on the parachutist.

(b) (i) State the initial value of the acceleration of the parachutist with correct units.

(ii)Explain why the acceleration decreases from A to B.

(iii) Explain why the parachutist falls at a constant speed after B.

(6 marks)

2.a) State what is meant by the mass of an object.

b) The mass of an object is 0.4kg. The gravitational field strength is 10 N/kg. Calculate the

size of the force acting downwards on the mass while it hangs freely

(3 marks)

3. The mass of air in a classroom is 500 kg. The density of air is 1.2 kg/m3.

(i) Define the term density.

(ii) Calculate the volume of air in the classroom.

(3 marks)

4. The diagram shows a boy of weight 740 N sitting on a see-saw. He sits 70 cm from the pivot.

(i) What is the force F, acting a distance of 210 cm needed to balance the see-saw?

(ii) State the principle that is used to help solve this problem (3 marks)

Multiple Choice - Select the correct answer

1. A body that is falling at terminal velocity has

A. Acceleration = 0

B. Increasing velocity

C. Resistive force acting upwards = 0

D. Resultant force greater than 0

2. Which of the following quantities is not a scalar quantity

A. Distance

B. Length

C. Velocity

D. Time

3. Which of the following is not true about a body in uniform circular motion?

A. It is accelerating

B. Speed of the body stays the same

C. Velocity of the body stays the same

D. Centripetal force is needed

4. An object moving 4.0 ms-1 increases its speed to 12.0 ms-1 in 3.0 seconds. How much distance did it cover during the 3 s time interval

A. 24 m

B. 12 m

C. 8.1 m

D. 16 m

5. An extension-load graph is plotted to show the result of increasing the load on a spring.

Which point marks the limit of proportionality for this spring?