Chapter 5

The diameter of a solid metal sphere is measured using a micrometer screw gauge. The mass of the sphere is 0.450 g. What is the density of the metal used to make the sphere?

• 965 kg m^–3

• 1340 kg m^–3

• 7720 kg m^–3

• 10 700 kg m^–3

The maximum pressure that granite rock can withstand is 2.0 × 10⁸ N m^–2. Above this pressure, the rock begins to flow like a liquid. The density of granite is 2.7 × 10³ kg m^–3. What would be the height of a pure granite mountain whose base is just beginning to flow?

• 3800 m

• 7600 m

• 37000 m

• 74000 m

The diagram shows two liquids, labelled P and Q, which do not mix. The liquids are in equilibrium in an open U-tube. What is the ratio density of P / density of Q?

• 1/2

• 2/3

• 3/2

• 2/1

A sealed cylindrical steel can is situated below the surface of water. What is the origin of the upthrust that acts on the can?

• The air pressure in the can is less than the water pressure outside the can.
• The average density of the air and steel is less than the density of water.
• The water pressure on the bottom of the can is greater than the water pressure on the top.
• The weight of displaced water acts upwards on the can.

A tennis ball is released from rest at the top of a tall building. Which graph best represents the variation with time t of the acceleration a of the ball, assuming that the effect of air resistance is not negligible?

• A

• B

• C

• D

A sphere falls from rest through the air. Which diagram shows the forces acting on the sphere when it is at the velocity corresponding to point P?

• A

• B

• C

• D

A ball is falling at terminal speed in still air. The forces acting on the ball are upthrust, viscous drag and weight. What is the order of increasing magnitude of these three forces?

• upthrust → viscous drag → weight
• viscous drag → upthrust → weight
• viscous drag → weight → upthrust
• weight → upthrust → viscous drag

A uniform beam is pivoted at P as shown. Weights of 10 N and 20 N are attached to its ends. The length of the beam is marked at 0.1 m intervals. The weight of the beam is 100 N. At which point should a further weight of 20 N be attached to achieve equilibrium?

• A

• B

• C

• D

Which pair of forces acts only as a couple on the circular object?

• A

• B

• C

• D

Forces are applied to a rigid body. The forces all act in the same plane. In which diagram is the body in equilibrium?

• A

• B

• C

• D