# Physics | Study Mode

Question 1
A
1 : 4
B
2 : 1
C
2 : 3
D
2 : 5
Explanation.

Let the forces be F1, and F2.
F1 = m1 a1 = 3 x 2 = 6N

F2 = m2 a2 = 1 x 9 = 9N

F1 : F2 = 6:9 = 2:3

Thus ratio of forces is 2: 3

Question 2
A
2 N
B
20 N
C
200 N
D
400 N
Explanation.

F = $$\frac{mv ^2}{r}$$

= $$m^2r$$

(Since V =r)

F = 10$$^{-2}$$ x 100$$^2$$ x 0.2

F =20 N

Question 3
A
1 . 25 x 104 W
B
2 . 50 x 104 W
C
1 . 25 x 106W
D
2 . 50 x 106 W
Explanation.

Power = Force x $$\frac{distance}{time}$$ = $$\frac{m(v - u)}{t} \times v$$

$$\frac{800(25 - 0)}{20} \times 25$$

= 2.5 x 10$$^{4}$$ watts

Question 4
A
2A
B
5A
C
10A
D
20A
Explanation.

The maximum current drawn by the cooker is given by;
I = $$\frac{P}{V}$$
I = $$\frac{\text{3000}}{200}$$
I = 15A
The fuse rating = I $$\times$$ 125% (the fuse is rated at 125% of the normal operating current)

Hence, the fuse rating = 15A $$\times$$ ($$\frac{125}{100}$$) = 18.75amps

Therefore, the best fuse is 20A.

Question 5
A
P1 > P2
B
P1 P2
C
P1 < P2
D
P1 = P2
Explanation.

As the temperature increases, the molecules in the gas move faster, impacting the gas's container more frequently and exerting a greater force. This increases the pressure. And similarly As the pressure goes up, the temperature also goes up. So the temperature and the pressure is directly proportional to each other. At a fixed point, temperature is kept constant. Hence, at this point, it can be deduced that $$P_{1} = P_{2}$$

Question 6
A
stationary and longitudinal
B
stationary and transverse
C
progressive and transverse
D
progressive and longitudinal
Explanation.

The vibrator is fixed at the end of the rope, hence, it is stationary. Also, the wave in this case, as well as the vibration are in the same direction, hence, it is longitudinal.

Question 7
A
9.0 x 10-13J
B
9.0 x 10-12J
C
9.0 x 10-11J
D
9.0 x 10-10J
Explanation.

In thermonuclear reactions,
Energy = mC2
m = Change in Mass
C = Speed of light
5.02 x 10-27 - 5.01 x 10-27 x [3 x 108]2
0.01 x 10-27 x 9 x 1016
E = 9.0 x 10-13J

Question 8
A
2.0J
B
4. 0 J
C
12.0 J
D
2.4 J
Explanation.
P = F/A => F = PA = PV/L
W = FD = (PV/L) x L = PV
= 2 x 105
(2 x 10-6 x 6)
= 2 x 105 x 1.2 x 10-5
= 2.4 J

Question 9
A
4.5
B
1.0
C
8.0
D
2.0
Explanation.
Efficiency = power out put/power input * 100/1
= power out put/ power + that due * 100/1
to internal resistance
=> 75/1 = 12R *100/1
12(R+r)
i.e 75/100 = 6/6+r => 75 (6+r) = 100/*6
i.e 450 + 75r = 600
75r =600 - 450
i.e r = 150/75 = 2
i.e r = 2

Question 10
A
3
B
2
C
1
D
6
Explanation.
1 = V/R = E/R+r , if r = 2
V = 3/5 E
=> 3E/5R = E/R+2
i.e 3E(R+2) = 5RE
3RE + 6E = 5RE
i.e 3R + 6 = 5R
6 = 5R - 3R
=> 2r = 6 i.e R = 6/2 = 3

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