# Physics (2017) | Study Mode

Question 11
A
80.00%
B
76.60%
C
66.70%
D
60.70%
##### Explanation
Efficiency = $$\frac{ma}{V.R}$$ x $$\frac{100}{1}$$

V.R = number of pulleys = 6

ma = $$\frac{\text{Load}}{\text{Effort}}$$ = $$\frac{200}{50}$$ = 4

Effiecieny = $$\frac{4}{6}$$ $$\times$$ 100 = 66.67%

Question 12
A

1

B

9

C

3

D

0.33

##### Explanation

Resistor connected in a parallel have an equivalence given by
$$\frac{1}{\text{Reff}}$$ = $$\frac{1}{3}$$ + $$\frac{1}{3}$$ + $$\frac{1}{3}$$

= $$\frac{1 + 1 + 1}{3}$$ = $$\frac{3}{3}$$ = 1

Reff = 1

Question 13
A
A compressor
B
A refrigerator
C
Air blower
D
Air conditioner
##### Explanation
Compressor is an instrument to supply air or other gas at increased pressure
Refrigerator is an appliance to keep things cold
Air blower is used to release air
Air conditioner is used to remove heat and maintain a stable temperature in an occupied space

Question 14
A
protons
B
electrons
C
ions
D
neutrons
##### Explanation
Isotopy is due to difference in mass number, what causes the difference is the difference in the number of neutrons present

Question 15
A
Balance wheel of a watch
B
Construction of steel rail lines
C
Construction of large steel bridges
D
Fitting of tyres on wheels
##### Explanation
Thermal expansion of a solid is majorly advantageous in the use of bimetallic strip in the balance of a watch so as not to lose time

Question 16
A
kgm
B
m
C
Jm
D
m$$^{-1}$$
##### Explanation
Moment of a force is the product of a force and the perpendicular distance from the line of action of the force
Moment = force $$\times$$ distance
= N $$\times$$ m
= Nm

Question 17
A
80.00%
B
76.60%
C
66.70%
D
60.70%

Question 18
A

10 cm

B

16 cm

C

5 cm

D

14 cm

##### Explanation

Magnification = $$\frac{\text{Length of camera}}{\text{distance of object from pin hole}}$$

m = $$\frac{12}{60}$$

= 0.2

Also magnification m = $$\frac{\text{Height of image}}{\text{Height of object}}$$

Height of image = m $$\times$$ height of object

= 0.2 $$\times$$ 70

= 14cm

Question 19
A

1:04

B

4:01

C

1:01

D

2:01

##### Explanation

H = mc

HP = HQ, P = 2q,

mP = $$\frac{1}{2}$$mQ

HP = mQCPP, also HQ = mQCQQ

Since HP = HQ

mPcPP = mQcPq

Putting in the conditions

$$\frac{1}{2}$$mQ $$\times$$ cP $$\times$$ 2Q = mQ $$\times$$ Q $$\times$$ cQ

cP = cQ

$$\frac{C_p}{C_Q}$$= $$\frac{1}{1}$$

= 1:1

Question 20
A

240v

B

340v

C

480v

D

57600v

##### Explanation

The relationship between the peak value and r.m.s value of electricity supply is given as

V$$_{r.m.s}$$ = $$\frac{V_o}{\sqrt{2}}$$

where Vo = peak voltage

Vo = V$$_{r.m.s}$$ x $$\sqrt{2}$$

= 240 x $$\sqrt{2}$$

= 339.5v

= 340v

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