# 1998 - JAMB Physics Past Questions and Answers - page 1

1

A bullet fired at a wooden block of thickness 0.15m manages to penetrate the block. If the mass of the bullet is 0.025kg and the average resisting force of the wood is 7.5 x 10

^{3}N, calculate the speed of the bullet just before it hits the wooden block.A

450ms

^{-1}B

400ms

^{-1}C

300ms

^{-1}D

250ms

^{-1}**Answer & Comments**

**correct option:**c

F = ma

Therefore, a = \(\frac{F}{m}\)

a = \(\frac{7.5 \times 10^{3}}{0.025}\)

a = 3 x 10

using V

V

Therefore V = 300 m/s

Users' Answers & CommentsTherefore, a = \(\frac{F}{m}\)

a = \(\frac{7.5 \times 10^{3}}{0.025}\)

a = 3 x 10

^{5}m/s^{2}using V

^{2}= U^{2}+ 2ax;V

^{2}= 0^{2}+ (2 x 3 x 10^{5}x 0.15)Therefore V = 300 m/s

2

The velocity of a sound wave at 27

^{o}C is 360ms^{-1}. Its velocity at 127^{o}C isA

120√3 ms

^{-1}B

240 ms

^{-1}C

240√3 ms

^{-1}D

720√3 ms

^{-1}**Answer & Comments**

**correct option:**c

Velocity \(\alpha \sqrt{temperature}\)

\(\frac{V_1}{V_2} = \sqrt{\frac{T_1}{T_2}}\)

therefore, \(\frac{360}{V_2} = \sqrt{\frac{27 + 273}{127 + 273}}\)

\(V_2 = 240\sqrt{3}\)m/s

Users' Answers & Comments\(\frac{V_1}{V_2} = \sqrt{\frac{T_1}{T_2}}\)

therefore, \(\frac{360}{V_2} = \sqrt{\frac{27 + 273}{127 + 273}}\)

\(V_2 = 240\sqrt{3}\)m/s

3

The physical quantity that has the same dimensions as impulse is

A

energy

B

momentum

C

surface tension

D

pressure

**Answer & Comments**

4

A ball is moving at 18ms

^{-1}in a direction inclined at 60^{o}to the horizontal. The horizontal component to its velocity isA

9√3ms

^{-1}·B

6√3ms

^{-1}·C

8√3ms

^{-1}·D

9ms

^{-1}·**Answer & Comments**

**correct option:**d

5

In free fall, a body of mass 1kg drops from a height of 125m from rest in 5s. How long will it take another body of mass 2kg to fall from rest from the same height? [g = 10ms

^{-1}·]A

5s

B

10s

C

12s

D

15s

**Answer & Comments**

**correct option:**a

In free fall, every object will reach the ground at same time

Users' Answers & Comments6

A ball of mass 0.15kg is kicked against a rigid vertical wall with a horizontal velocity of 50ms

^{-1}. If it rebounced with a horizontal velocity of 30ms^{-1}, Calculate the impulse of the ball on the ball · ·A

3.0Ns

B

4.5Ns

C

7.5Ns

D

12.0Ns

**Answer & Comments**

7

The force of attraction between two point masses is 10

^{-4}N when the distance between them is 0.18m. If the distance is reduced to 0.06m, calculate the force.A

1.1 x 10

^{-5}NB

3.3 x 10

^{-5}NC

3.0 x 10

^{-4}ND

9.0 x 10

^{-4}N**Answer & Comments**

**correct option:**d

F \(\alpha \frac{1}{r^2}\)

therefore, \(\frac{F_1}{F_2}\) = \(\frac{r_1}{(r_2)^2}\)

\(\frac{10^{-4}}{F_2}\) = \(\frac{(0.06)^2}{(0.18)^2}\)

F = 9 x 10

Users' Answers & Commentstherefore, \(\frac{F_1}{F_2}\) = \(\frac{r_1}{(r_2)^2}\)

\(\frac{10^{-4}}{F_2}\) = \(\frac{(0.06)^2}{(0.18)^2}\)

F = 9 x 10

^{-4}N8

A uniform meter rule weighing 0.5N is to be pivoted on a knife-edge at the 30cm-mark. where will a force of 2N be placed from the pivot to balance the meter rule?

A

95cm

B

25cm

C

20cm

D

5cm

**Answer & Comments**

**correct option:**b

9

A man whose mass is 80kg climbs a staircase in 20s and expends power of 120W. Find the height of the staircase.[g = 10ms

^{-2}]A

1.8m

B

2.0m

C

2.5m

D

3.0m

**Answer & Comments**

**correct option:**d

Power x time = mgh

120 x 20 = 80 x 10 x h

2400 = 800h

making h the subject of formula,divide both side by 800

\(\frac{2400}{800}\) = h

h = 3m

Users' Answers & Comments120 x 20 = 80 x 10 x h

2400 = 800h

making h the subject of formula,divide both side by 800

\(\frac{2400}{800}\) = h

h = 3m

10

A parachute attains a terminal velocity when

A

its density is equal to the density of air

B

the viscous force of the air and the upthrust completely counteract its weight

C

it expands as a result of reduced external pressure

D

the viscous force of the air is equal to the sum of the weight and upthrust

**Answer & Comments**

**correct option:**b