Correct Answer: A. 1.9J

Explanation

P.E = \(\frac{1}{2}\)Fe

= \(\frac{1}{2}\)\(\frac{F}{K}\)

= \(\frac{1}{2}\) x \(\frac{75 \times 75}{1500}\)

= 1.9J

Correct Answer: C. 200N

Explanation

F = ma = \(\frac{mv}{t} = \frac{5 \times 10^{-2} \times 4 \times 10^{3}}{1}\)

= 200N

Correct Answer: A. 250W

Explanation

P=\(I^2R= 25\times 10=250W\)

Correct Answer: C. 66.3V

Explanation

(a)(i) Refraction of a wave is the change in the direction of the wave as it moves from one medium to another of different density.

(ii) Critical angle is the angle of incidence in the denser medium beyond which total internal reflection occurs.

(b) (i) The conditions necessary for total internal reflection of wave to occur are:-

- The wave must be travelling from a denser medium to a less dense medium

- The angle of incidence of the wave in the denser medium must be greater than the critical angle of the medium.

(ii) The conditions necessary for interference pattern to be formed are:-

- Two or more sources must be involved.

- The distance between the sources must be of the order of the wave length of the waves

(c) V = \(f \lambda\)

F = \(\frac{v}{\lambda} = \frac{3.6}{0.45}\)

= 8.0Hz

(d) (i)

(ii) n = \(\frac{sin i}{sin r}\)

r = sin\(^{-1} (\frac{sin i}{n})\)

= sin\(^{-1} (\frac{sin 30}{1.5})\)

= 19.5\(^o\)

Deviation = i - r = 30 - 19.5

= 10.5\(^o\)

Explanation

(a) Principle of conservation of linear momentum states that if two or more bodies collide in a closed system, the total momentum after the collision is equal to the total momentum before the collision.

(b) The principle of action of a propelled rocket is that gas burnt within the combustion chamber of the rocket engine is expelled downwards through the exhaust (tail nozzle) at very high speed, hence an equal and opposite momentum is given to the rocket which moves the rocket upward.

(c) The motion is not simple harmonic because:

-there is no equilibrium position

-acceleration of the ball is not directly proportional to displacement

-acceleration of the ball is not directed towards a fixed point.

(d)(i) Both balls will hit the ground at the same time.

(ii) All free falling objects fall at the same rate because they are pulled towards the earth by gravity and accelerate at a constant rate.

(e)(i) Charge in momentum = m(v-u)

= 0.10(13 - 17) = 3 kgms\(^{-1}\)

(ii) Average force F = \(\frac{\text{change in momentum}}{\text{time}}\) = \(\frac{3}{0.15} = 20N\)

Correct Answer: D. 60V

Explanation

Voltage across 5Ω resistor = IR = 2 × 5 = 10V

Since voltage in a parallel connection is the same, voltage across 10Ω is also 10V

Current flowing across the 10Ω resistor

I = V/R = 10/10

Current I= 1A

Total current flowing = 2 + 1 = 3A

Voltage across 20Ω resistor = IR

= 3 × 20

= 60V

Correct Answer: C. The molecules of matter are not in constant motion

Correct Answer: A. 1600

Correct Answer: A. 3 day

Explanation

The equation that establishes a relationship between the amountleft undecayed,

A, the initial amount, A0, and thenumber of half-lives that pass in a period of time t looks like this:

\(\frac{1}{2^n} * A_0 = A\)

\(\frac{1}{2^n} * 120 = 15\)

\(\frac{1}{2^n}\) = \(\frac{15}{120}\)

\(\frac{1}{2^n}\) = \(\frac{1}{8}\)

\(\frac{1}{2^n}\) = \(\frac{1}{2^3}\)

\(2^n = 2^3\)

n = 3