1. The stability of a bus is tested by tilting it on a ramp. The diagram shows a bus that is just about to topple over.

Where is the centre of mass of the bus? (15 marks)

□2. The diagram shows a uniform half-metre rule balanced at its mid-point.

What is the weight of the metal block?

A 50 N B 75 N C 100 N D 150 N (15 marks) □3. A piece of uniform card is suspended freely from a horizontal pin.

At which of the points shown is its centre of gravity? (15marks)

□4. The diagram shows a boy of weight 500 N sitting on a see-saw. He sits 2.0 m from the pivot.

1 of 2 班級(Class):________ 學號(No):__________

What is the force F needed to balance the see-saw?

A 250 N B 750 N C 1000 N D 3000 N (15marks) □5. A spring balance is calibrated to give readings in newtons.

The graph shows how the length of the spring varies with the load.

A load causes the spring of the balance to extend by 3 cm.

What is the balance reading?

A 3 N B 5 N C 10 N D 15N (15marks) □6.

a) State two reasons why Position A is more unstable than Position C. (10marks)

b) What is meant by unstable ? (5marks)

c) What is meant by stable? (5marks)

d) What is meant by Centre of Gravity ? (5marks)

2 of 2 班級(Class):________ 學號(No):__________

A

BC

C.G.