WAEC Physics Past Questions & Answers - Page 231

1,151.

A solid plastic cube of side 0.2m is submerged in a liquid density of 0.8kg\(m^{-3}\). Calculate the upthrust of the liquid on the cube (g=10\(ms^{-2}\)

A.

0.064N

B.

0.025N

C.

0.016N

D.

0.008N

E.

0.003N

Correct answer is A

Upthrust = Volume of fluid displaced =vpg =0.2 x 0.2 x 0.2 x0.8 x 10= 0.064N

1,153.

Two forces 3N and 4N act on a body in directions due north and due east respectively. Calculate their equilibrant

A.

5N 53° east of North

B.

5N 53° west of the south

C.

5N 37° north of east

D.

7N 37° west of North

E.

7N 37° south of west

Correct answer is C

No explanation has been provided for this answer.

1,154.

Two blocks of the same dimension, one steel and the other wooden are dropped simultaneously from the same height. If they fall freely neglecting air resistance the?

A.

Two blocks hit the ground simultaneously because they have the same acceleration

B.

Two blocks reach the ground at the same time because their dimensions are the same

C.

Wooden block being lighter than the steel block reaches the ground first

D.

Steel block reaches the ground first because it is denser than the wooden block

E.

Steel block takes half as much time as the wooden block to reach the ground because it is more massive than the wooden block

Correct answer is A

An object falling without air resistance or friction is defined to be in free-fall. 

The acceleration of free-falling objects is therefore called the acceleration due to gravity.

It is because the acceleration due to gravity is constant for all objects regardless of the mass, neglecting air resistance.

1,155.

An object falls freely from a height of 25m onto the roof a building 5m high. Calculate the velocity with which the object strikes the roof (g=10\(ms^{-2}\)

A.

17.3\(ms^{-2}\)

B.

20\(ms^{-2}\)

C.

24.5\(ms^{-2}\)

D.

125\(ms^{-2}\)

E.

200\(ms^{-2}\)

Correct answer is B

\(v^2=u^2 +2as =0 +2\times(25-5)\\ v^2 =0+20\times 20=400;v =\sqrt{400}= 20(ms^{-2}\)