JAMB Physics Past Questions & Answers - Page 187

931.

Mercury is a better barometric fluid than water because

i. it needs no colouring
ii. its density is many times greater than that of water
iii. it does not wet glass
iv. it has a high vapour pressure
v. it has a high boiling point.

Which of the above statements are true?

A.

i and ii only

B.

i, ii and iii only

C.

iii and iv only

D.

iv and v only

E.

iii, iv and v only

Correct answer is B

The advantages of use of mercury in a barometer are :

  1. its density is very high.
  2. it has low vapor pressure.
  3. its rate of evaporation is not very high.
  4. it neither wets nor sticks to glass.
  5. its surface is shining and opaque.

932.

A machine gun with a mass of 5kg fires a 50g bullet at speed of 100ms-1. The recoil speed of the machine gun is

A.

0.5 msec-1

B.

1.5 msec-1

C.

1 msec-1

D.

2 msec-1

E.

4 msec-1

Correct answer is C

Gun momentum = bullet momentum

5 x v = 0.05 x 100

v = 1 msec-1

933.

An ice cube floats in a glass of water filled to the brim. What happens when the ice melts?

A.

The water level remains the same

B.

there is a drop in the level of water in the glass due to condensation on its outside

C.

the water in the glass overflows

D.

the level of water drops because melted ice occupies less volume

E.

none of the above is correct

Correct answer is A

The law of flotation states that a floating object displaces its own weight of the fluid in which it floats. This implies that no extra volume of water is added as the ice melts.

934.

A piece of rubber 10cm long stretches 6mm when a load of 100N is hung from it. What is the strain?

A.

60

B.

6

C.

6 x 10-2

D.

6 x 10-3

E.

0.6

Correct answer is C

Strain = \(\frac{\Delta L}{L}\)

Extension produced = 6mm or 0.6cm

Original length = 10cm

= \(\frac{0.6}{10}\)

= 0.06 or 6 x 10\(^{-2}\)

935.

A palm fruit dropped to the ground from the top of a tree 45m tall. How long does it take to reach the ground? (g = 10ms-2)

A.

9s

B.

4.5s

C.

6s

D.

7.5s

E.

3s

Correct answer is E

Using the equation of motion

S = ut + \(\frac{1}{2}\)at2

45 = (0 x t) + (\(\frac{1}{2}\) x 10 x t2)

t = 3s