JAMB Physics Past Questions & Answers - Page 189

941.

A weight of 1000 grams hangs from a lever 20cm to the fulcrum. At the left is a 500-gram weight 20cm from the fulcrum, and a 200-gram weight x cm away from the fulcrum. What is the value of x that will make the lever balanced?

A.

50cm

B.

20cm

C.

10cm

D.

30cm

E.

70cm

Correct answer is D

Taking moment about F,

200(X + 20) + (500 x 20) = (1000 x 20)

200X + 4000 + 10000 = 20000

200X + 14000 = 20000

200X = 20000 - 14000

200X = 6000

X = 30cm

942.

It is known that a neutron exists in a light atomic nucleus. Which of the following also exists in the nucleus?

A.

an electron

B.

a \(\beta\)-particle

C.

an \(\alpha\)-particle

D.

a proton

E.

an atom

Correct answer is D

No explanation has been provided for this answer.

943.

A body is released from rest and allowed to fall freely from a given height under gravity. The kinetic energy at its half-way point is?

A.

a little above half of its initial energy

B.

a little below half of its initial energy

C.

a half of its initial energy

D.

a little above its initial energy

E.

a little below its initial energy

Correct answer is C

Energy for complete distance is twice the energy for half  the distance

944.

On which of the following is the operation of a moving coil galvanometer based?

A.

Magnetic effect of electric current

B.

Electromagnetic induction

C.

Chemical reaction produced by electricity

D.

Force on current carrying conductor in a magnetic field

E.

Electrical energy and power

Correct answer is D

No explanation has been provided for this answer.

945.

The speed of light in air is 3 x 108ms-1. If the refractive index of light from air-to-water is \(\frac{4}{3}\), then which of the following is the correct value of the speed of light in water?

A.

4 x 108ms-1

B.

2.25 x 108ms-1

C.

\(\frac{4}{9}\) x 108ms-1

D.

2.25 x 102ms-1

E.

4.33 x 108ms-1

Correct answer is B

Air to water = \(\frac{\text{speed in air}}{\text{speed in water}}\)

\(\frac{4}{3}\) = \(\frac{3 \times 10^8}{V}\)

4V = 3(3 x 108)

V = \(\frac{3(3 \times 10^8)}{4}\)

V = 2.25 x 108ms-1