JAMB Physics Past Questions & Answers - Page 157

781.

For a best result using temperature to achieve an accurate measurement, it is best to use

A.

Mercury thermometer

B.

gas thermometer

C.

clinical thermometer

D.

alcohol thermometer

Correct answer is B

A gas thermometers are more besting use to achieve an accurate temperature than others, such as liquid in glass thermometers such as mercury, clinical and alcohol thermometer

782.

If the mechanical advantage of a machine is 4. What is its ratio for LOAD to EFFORT?

A.

4:01

B.

1:04

C.

5:01

D.

2:01

Correct answer is A

Mechanical advantage (M.A) of a machine is the ratio of its load to effort

Mathematically

Mechanical advantage (M.A) = Load (L) ÷ Effort (E)

In symbol M.A = L/E

Note:Mechanical (advantages has no S.I unit)

If M.A = 4 then,

L/E = 4/1

The ratio of load to effort = 4 : 1 respectively

783.

If the velocity ratio of a machine is 5. What is its ratio of x and y?

A.

2 : 5

B.

1 : 5

C.

5 : 1

D.

3 : 1

Correct answer is C

Velocity Ratio (V.R) = distance moved by the effort (x)÷ distance moved by the load (y)

i.e. V.R = x/y

v. R = 5, x/y = ?

i.e x/y = 5/1; , where x = 5, y = 1

x : y = 5 : 1

784.

If a ball released from a height of 20m, How long would it take the ball to reach the ground? (assumes g = 10m/s)

A.

2sec

B.

3sec

C.

35sec

D.

2.4sec

Correct answer is A

Using the equation

S = ut + ½ gt2

H = s = 20m, t = ?

G =10m/s2, u = 0m/s

20 = 0 × t × ½ × 10 t

20 = 5t

i.e 5t2 = 20

t = 20/5 = 4

t = 4 (squaring both sides)

√ t2 = √4

= 2sec

∴ t = 2sec

785.

A zinc has a heat capacity of 40 J/K, what is the mass of the zinc, given that the specific heat of zinc is 380 J/kg k

A.

0.11kg

B.

0.12kg

C.

0.13kg

D.

0.14kg

Correct answer is A

Heat capacity (o) = mass (kg) specific heat of a substance (C2)

i.e Q = MC

where Q = 40 J/L, m = ?(380 J/Kgk)

40 = m × 380

m = 0.11kg (Approx)