WAEC Physics Past Questions & Answers - Page 142

706.

A car of mass 800kg moves from rest on a horizontal track and travels 60m in 20s with uniform acceleration. Assuming there were no frictional forces, calculate the accelerating force

A.

240.0N

B.

800.0N

C.

1600.00N

D.

2400.0N

Correct answer is A

S = at + \(\frac{1}{2} at^2\)

60 = 0 x 20 + \(\frac{1}{2}\) x a x 20

a = \(\frac{3}{10}\)m/s2

F = ma = 800 x \(\frac{3}{10} = 240N\)

707.

An external force of magnitude 100N acts on a particle of mass 0.15kg for 0.03s. Calculate the change in the speed of the particle

A.

50ms-1

B.

25ms-1

C.

20ms-1

D.

5ms-1

Correct answer is C

a = \(\frac{F}{m} = \frac{100}{0.15} = 666.7\)

v = u + at

= 0 + 66.7 x 0.03

= 20m/s2

708.

A block of mass 4.0kg causes a spiral spring to extend by 0.16m from its unstretched position. The block is removed and another body of mass 0.50kg is hung from the same spiral spring. If the spring is then stretched and released, what is the angular frequency of the subsequent motion? [g = 10 ms -2]

A.

10\(\sqrt 5\) rads-1

B.

5\(\sqrt 2\) rads-1

C.

5 rads-1

D.

\(\sqrt 5\) rads-1

Correct answer is A

K = \(\frac{F}{e} = \frac{4}{0.16} = 250\)

F = \(\frac{1}{T} = \frac{1}{2 \pi \frac{\sqrt{m}}{k}}\)

= \(\frac{1}{2 pi \frac{\sqrt{0.5}}{250}}\)

= 10\(\sqrt{5}\)

709.

A swinging pendulum between the rest position and its maximum displacement possesses

A.

Kinetic energy only

B.

potential energy only

C.

gravitational energy only

D.

both kinetic and potential energy

Correct answer is D

No explanation has been provided for this answer.

710.

A body accelerates uniformly from rest at 2ms-2. Calculate the magnitude of its velocity after travelling 9m

A.

4.5 ms-1

B.

6.0ms-1

C.

18.0-1

D.

36.0-1

Correct answer is B

v = \(\sqrt{U^2} + 2as = \sqrt{0^2} + 2 \times 2 \times 9 = 6\)m/s