A scientist looking for meteorites on Antarctica
finds an irregularly shaped rock and
he wants to determine its density. He determines that the rock’smass 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 only2mm? Explain
your answer.
Thescientist now submerges the rock in a tub of water. He nowdetermines 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 (Ï=789kg/m3), would he havefound a larger or smaller effective weight when the rock issubmerged?
Explain your answer.
