JAMB Physics Past Questions & Answers - Page 452

2,256.

Which of the following consists entirely of vector quantities?

A.

Velocity, magnetic fulx and reaction

B.

Tension, magnetic flux and mass

C.

Displacement, impulse and power

D.

Work, pressure and moment

Correct answer is A

No explanation has been provided for this answer.

2,257.

The efficiency of a machine is always less than 100% because the

A.

work output is always greater than the work input

B.

load lifted is always greater than the effort applied

C.

effort applied is always greater than the load lifted

D.

velocity ratio is always greater than the mechanical advantage

Correct answer is D

No explanation has been provided for this answer.

2,258.

I. The earth is not spherical but elliptical in shape
II. Variation in latitude and longitude
III. Rotation of the earth on its axis
IV. Variation in the density of the earth

On which combination of the above does the weight of an object vary on the earth's surface?

A.

I, II, III and IV

B.

III and IV only

C.

I, II and III only

D.

I and II only

Correct answer is B

A person can weigh differently at various place on Earth because of the fluctuations in Earth's gravity,

because the planet is not perfectly spherical or uniformly dense and its rotation.

2,259.

The resultant of two forces acting on an object is maximum if the angle between them is

A.

45°

B.

C.

90°

D.

180°

Correct answer is B

The resultant of two forces acting on an object is maximum when the angle between them is zero, during which the tow forces are parallel and pointing in the same direction

2,260.

If a spherical metal bob of radius 3cm is fully immersed in a cylinder containing water and the water level rises by 1cm, what is the radius of the cylinder?

A.

12cm

B.

1cm

C.

3cm

D.

6cm

Correct answer is D

If the bob is fully immersed in the water, then the volume of water displaced will be equal to the volume of the bob = 4/3πr3, where r is the radius of the bob.
This volume of water in the cylinder = πr2l, where r = radius of the cylinder, and l = level of water rose in the cylinder.

Therefore, π x r2 x l = 4/3 x π x 33

Then r2 = 36
r = √36
r = 6cm