JAMB Physics Past Questions & Answers - Page 269

1,341.

A piece of wood of mass 40g and uniform cross-sectional area of 2cm2 floats upright in water. The length of the wood immersed is

A.

30cm

B.

40cm

C.

20cm

D.

2cm

Correct answer is C

Mw displaced = 40g

density = \(\frac{mass}{\text{area x height}}\)

I = \(\frac{40}{2\times h}\)

h = 20cm

1,342.

Which of the following devices are used to measure pressure?

i. Aneroid barometer.
ii. hydrometer.
iii. hygrometer.
iv. manometer.

A.

i and iii

B.

ii and iii

C.

iii and iv

D.

i and iv

Correct answer is D

No explanation has been provided for this answer.

1,343.

A block-and-tackle system is used to lift a load of 20N through a vertical height of 10m. if the efficiency of the system is 40%, how much work is done against friction?

A.

80J

B.

120J

C.

300J

D.

500J

Correct answer is C

Efficiency = \(\frac{output}{input}\) x 100

40 = \(\frac{20\times10}{input}\) x \(\frac{100}{1}\)

input = 500J

work against friction = input - output

= 500 - 200 = 300J

1,344.

A thin film of liquid is trapped between two glass plates. The force required to pull the plates apart will increase if the

A.

surface tension of the liquid is reduced

B.

perpendicular distance between the plates is increased

C.

area of the liquid surface in contact with the plates is increased

D.

pressure of the air is decreased

Correct answer is C

No explanation has been provided for this answer.

1,345.

Two points on a velocity time-graph have coordinates (5s, 10ms-1) and (20s, 20ms-1). Calculate the mean acceleration between the two points

A.

0.67ms-1

B.

0.83ms-1

C.

1.50ms-1

D.

2.00ms-1

Correct answer is A

a = \(\frac{v - u}{\Delta t}\)

a = \(\frac{20 - 10}{20 - 5}\)

a = 0.67ms-1