Question

A scientist looking for meteorites on Antarctica

finds an irregularly shaped rock and

he wants to determine its density. He determines that the rock’s mass in air is 50

kg.

The Young’s modulus of steel is 200

·

10

9

Nm

-

2

. The ultimate strength of steel is

500

·

10

6

Nm

-

2

.

Q 4(a)

[5

Marks]

He hangs the rock from a

2

-

metre

-

long

steel cable with a diameter of 1

cm. Calculate

the strain and change in length of the cable

.

Q 4(b)

[5 Marks]

What would happen if he had used a cable with a diameter of only 2mm? Explain

your answer.

Thescientist now submerges the rock in a tub of water. He now determines the effective weight to be 38.5kg.

Q 4(c)

[5

Marks]

Calculate the volume and density of the rock

.

Q 4(d)

[5 Marks]

If the scientist had used alcohol (ρ=789kg/m3), would he have found a larger or smaller effective weight when the rock is submerged?

Explain your answer.

Answer 1