# Physics 2018 | Study Mode

Question 31
A
$$1.11\times 10^{-7} N$$ towards P
B
$$1.11\times 10^{-7} N$$ towards Q
C
$$9.26\times 10^{-8} N$$ towards P
D
$$9.26\times 10^{-8} N$$ towards Q
##### Explanation

$$F= \frac{Gm_{1}m_{2}}{r^{2}}$$

$$m_{1} = 100kg$$

$$m_{2} = 20kg; r =1.2m$$

$$G= 6.67\times 10^{-11}$$

$$F = \frac{6.67\times 10^{-11}\times 100\times 20}{(1.2)^{2}} = 9.26\times 10^{-8}$$

The acceleration of each object is inversely proportional to the mass, the lighter object will move a bit faster, hence. the force will act in the direction of Q.

Question 32
A
50V
B
100V
C
200V
D
400V
##### Explanation

The ideal transformer (either step-up or step-down) works with the equation:

$$\frac{V_{s}}{V_{p}} = \frac{N_{s}}{N_{p}} = \frac{I_{p}}{I_{s}}$$

where $$V_{s}$$ and $$V_{p}$$ are the voltages applied to the secondary and the primary respectively

$$N_{s}$$ and $$N_{p}$$ are the number of turns on the secondary and primary coils respectively

$$I_{p}$$ and $$I_{s}$$ are the currents flowing in the primary and secondary coils respectively.

$$\frac{V_{s}}{100} = \frac{200}{100}$$

$$V_{s} = \frac{200\times 100}{100} = 200V$$

Question 33
A
increases
B
decreases
C
remain the same
D
decreases and later increases
##### Explanation

The velocity ratio and therefore, the mechanical advantage of an inclined plane system increases as $$\theta$$ decreases and vice-versa.

Question 34
A
doubled
B
quartered
C
halved
D
##### Explanation

Given $$K_{1}$$ = $$\frac{mv^{2}}{2}$$.

When v is halved, we have

$$K_{2}$$ = $$\frac{m\times (\frac{v}{2})^{2}}{2}$$

= $$\frac{K_{1}}{4}$$

Hence, the initial kinetic energy is quartered.

Question 35
A
250$$ms^{-1}$$
B
625$$ms^{-1}$$
C
1200$$ms^{-1}$$
D
1500$$ms^{-1}$$
##### Explanation

The fundamental frequency $$(f_{0})$$ = $$\frac{v}{2l}$$

$$f_{0} = 150Hz; l =400cm = 4m$$

$$150 = \frac{v}{2\times 4}$$

$$v = 150 \times 8 = 1200ms^{-1}$$

Question 36
A
4
B
3$$\frac{1}{2}$$
C
2$$\frac{1}{2}$$
D
2
##### Explanation

Question 37
A
resistance box
B
standard resistor
C
shunt resistor
D
multiplier resistor
##### Explanation

Question 38
A
The electrolyte does not need attention
B
It can be recharged
C
It has low internal resistance
D
It has a much longer life than lead-acid accumulator
##### Explanation

Question 39
A
live, neutral and earth
B
neutral, earth and live
C
earth, live and neutral
D
earth, neutral and live

Question 40
A
I only
B
I and II only
C
II and III only
D
I, II and III
##### Explanation

Capacitors pass AC but block DC signals (when charged up to the applied DC voltage), they are often used to separate the AC and DC components of a signal. Capacitors are also primarily used to store energy.

Try this quiz in in E-test/CBT Mode
switch to