JAMB Physics Past Questions & Answers - Page 392

1,956.

When cold water is poured on a can containing hot water, the can collapses because the?

A.

steam condeses and occupies the partial vacuum in the can

B.

external air pressure counter balances the pressure within the can

C.

steam expands to occupy the vacuum remaining in the can

D.

external pressure becomes greater than the pressure within the can.

Correct answer is D

Cold water reduces the temperature of the hot water inside the can causing the contraction of the hot water. This reduces the pressure inside the can and the can collapses due to the external greater expression.

1,957.
1,958.

A spring of force constant 500 NM-1 is compressed such that its length shortens by 5cm. The energy stored in the spring is?

A.

0.625 J

B.

6.250 J

C.

62.500 J

D.

625.000 J

Correct answer is A

Energy stored in a spring = (1)/2 K e2 = (1)/2 x 500(0.05)2 = 0.625J

1,959.

A motorcycle of mass 100kg moves round in a circle of radius 10m with a velocity of 5 ms-1. find the coefficient of friction between the road and the tyres.

A.

25.00

B.

2.50

C.

0.50

D.

0.25

Correct answer is D

F = (mv)2/r = (100 x 5)2 = 250N
R = mg = 100 x 10 - 1000N
coefficient of friction,
µ = (F)/R = (250)/1000 = 0.25

1,960.

counting of currency notes with moist fingers is based on the principles of?

A.

diffusion

B.

cohesion

C.

adhesion

D.

viscosity

Correct answer is C

since currency and finger contain unlike molecules, the force involved is adhesion