JAMB Physics Past Questions & Answers - Page 41

201.

The force required to make an object of mass m, travelling with velocity v, turn in a circle of radius r is

A.

\(\frac{mv^2}{r}\)

B.

\(\frac{mr^2}{x}\)

C.

\(\frac{mr}{v}\)

D.

\(\frac{mv}{r^2}\)

Correct answer is A

No explanation has been provided for this answer.

202.

A few grains of table salt were put in a cup of cold water, kept at constant temperature and left undistributed. Eventually all the water tested salty. This action is due to?

A.

convection

B.

osmosis

C.

capillarity

D.

diffusion

Correct answer is D

Diffusion is the tendency of molecules to migrate and fill an empty space due to their random thermal motions.

in diffusion, the diffusing molecules move from the places where their concentration high to places where their concentration is low.

203.

Which of the following readings cannot be determined with a meter rule?

A.

2.56cm

B.

2.25cm

C.

2.50cm

D.

2.05cm

Correct answer is A

Meter rule has a reading accuracy of 0.5mm or 0.05cm, thus measurement is M ± 0.05cm i.e 2.00, 2.05, 2.50, 2.55 etc.
The reading that cannot be read is 2.56cm.

204.

A body was slightly displaced from its equilibrium position. Which one of the following is a condition for its stable equilibrium

A.

an increase in the kinetic energy of the body

B.

an increase in the potential energy of the body

C.

a decrease in the kinetic energy of the body

D.

an increase in the height of the body

Correct answer is B

Stable equilibrium brings about increase in potential energy as the height rises after displacement.

205.

A mass of 0.5kg is whirled in a vertical circle of radius 2m at a steady rate of 2 rev/s. Calculate the centripetal force

A.

164N

B.

160N

C.

158N

D.

172N

Correct answer is C

ω = 2πF = 2π × 2 = 4πrad\(^{-1}\)
Centripetal force = mrω\(^2\)
⇒ 0.5 × 2 × (4π)\(^2\)
⇒ 157.75N

Approximately = 158N.