2019 Physics WAEC (WASSCE) Essay Past Questions (Paper 2)

Question 1

A stone of mass 20 g is released from a catapult whose rubber is stretched through 5 cm. If the force constant of the rubber is 200 Nm^-1 , calculate the speed with which the stone leaves the catapult.

Solution

Work done by elastic material = The kinetic energyEnergy is the ability to do work. Energy exists in several forms such as heat, kinetic or mechanical energy, light, potential energy, and electrical energy. Units of Energy: The SI unit... More of the moving stone

Ke² = \(\frac{1}{2} \scriptsize MV^2\)

e = 5cm × \(\frac{1m}{100} \scriptsize = 0.05\: m\)

Mass = \(\scriptsize 20g \: \times \: \normalsize \frac{kg}{1000}\)

Mass = 0.02 kg

Substituting

200 × (0.05)² = \(\frac{1}{2} \scriptsize\: \times \: 0.03 \: \times V^2\)

0.5 = 0.01 × V²

V² = \(\frac{0.5}{0.01}\)

V² = 50

V = \(\scriptsize \sqrt{50}\)

V = 7.07 m/s

Question 2

(a)

The diagram above illustrates a projectile motion. Identify each of the physical quantities labelled P, β, H and R.

Solution

Height (H) ⇒ Maximum vertical Height attained by the projectile.

P – is the initial velocity of the projectile

R – is the total horizontal distance covered by the projectile during flight.

β – Initial angle the projectile is launched to the horizontal plane.

(b)

Write an equation to show the relationship between P, g and R_max , where g is the acceleration due to gravity and R_max is maximum R.

Solution

R = \(  \frac{P^2 sin (2 \beta)}{g}\)

when R is maximum, β = 45

R_max = \(\frac{P^2}{g}\)

Question 3

State three observable phenomena in which waves behave like a particle.

Solution

i. Photo-electric effect – when ultraviolet shines on some metals and
photoelectrons are emitted. The light is acting as a particle.

ii. Thermonic equation.

iii. Compton effect.