## Physics (2018) Study Mode

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Question 51
A
electromotive force
B
electric potential difference
C
electric energy
D
kinetic energy
Explanation.

Electric potential difference: work needed per unit of charge to move a test charge between the two points.
Electric energy: energy derived from electric potential energy.
Kinetic energy: moving energy

Question 52
A
0Nm
B
3Nm
C
7Nm
D
10Nm
Explanation.

Moment = Force × Distance
= 5N x 2m
= 10Nm

Question 53
A
0.3?
B
3.3?
C
3.6?
D
4.8?
Explanation.

Power delivered to head lamp = $$\frac{V_2}{R}$$

= 40W

R = $$\frac{V_2}{40}$$

= $$\frac{(12 × 2)}{40}$$

= 3.6Ω

Question 54
A
15$$^o$$
B
18$$^o$$
C
22$$^o$$
D
24$$^o$$
Explanation.

X = $$\frac{4}{3}$$ r = ?

Shell’s law:. 7 = $$\frac{Sin 2^0}{ Sin r^0}$$

$$\frac{V}{g}$$ = $$\frac{Sin 30^0}{Sin r^0}$$

Sin$$r^0$$ = $$\frac{3 Sin 30^0}{4}$$

Sin $$r^0$$ = 0.375

R $$^o$$ = Sin-1 (0.375)

R $$^o$$ = 22.02 $$^o$$

R $$^o$$ = 22 $$^o$$

Question 55
A

15.0$$^o$$C

B

45.0$$^o$$C

C

52.5$$^o$$C

D

60.0$$^o$$C

Explanation.

Power = 1kw=100W

Time = 2mins = 2 × 60 = 120secs

Energy = power × time

1000 × 120 = 120,000J

Energy = mc(θ$$_2$$ – θ$$_1$$)

120,000 = 2 × 4000(θ$$_2$$ – θ$$_1$$)

θ2 = 30 + 15 = 45 $$^o$$ C

Question 56
A
Electrons
B
Ion
C
Neutron
D
Proton
Explanation.

Ion: an atom with a net electric charge due to loss or gain of one or more electrons
Neutron: a subatomic particle of about the same mass as a proton without electric charge.
Proton: a subatomic particle with a positive charge

Question 57
A
total kinetic energy of its molecules
B
average kinetic energy of its molecules
C
average speed of its molecules
D
maximum speed of its molecules
Explanation.

[Average kinetic energy of its molecules]

Question 58
A
Impulse
B
Momentum
C
Inertia
D
Friction
Explanation.

An impulse is equal to the net force on the object times the time period over which this force is applied. Impulse is derive from the equation F = ma, which comes from Newton's second law of motion

Question 59
A
Diffusion
B
Brownian motion
C
Diffraction
D
Crystallization
Explanation.

Diffusion is the net movement of molecules/atoms from a region of high concentration to low concentration.

Brownian motion is the erratic random movement of microscopic particles in a field.

Diffraction is the various phenomena that occur when a wave encounters an obstacle.

Question 60
A
50km
B
25km
C
15km
D
10km
Explanation.

Distance = speed × time

= $$\frac{(\frac{100 \times 103}{3600})}{15 \times 60}$$

= 25km

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