2017 - WAEC Physics Past Questions and Answers - page 2
The angle at which a projectile must be fired to cover maximum range is
The formula is \(\frac{v^{2}sin2\theta}{g}\)
And the sine graph is highest at 1 with its inverse as 90°. Hence, \(2\theta\) = 90°
\(\theta\) = 45°
A body can undergo the following types of motion except
Relative motion is the calculation of the motion of an object with regard to some other moving object. Hence, relative motion is not a type of motion.
Which of the following graphs correctly represents the relationship between the kinetic energy (K.E) and the displacement (d) from point of release of a swinging pendulum bob?
Ice of mass 50g at 0°C was completely melted by 70% of the total heat energy supplied. Calculate the total heat energy supplied [Specific latent heat of fusion of ice = 336\(Jg^{-1}\)]
The quantity of heat needed to melt ice = mL (where m is the mass of ice and L is the specific latent heat of fusion of ice)
Q = \(50 \times 336 = 16800J\) but this is 70% of the total heat supplied so that we have,
70% total heat = 16800J
\(\frac{70}{100} heat = 16800J\)
Total heat supplied = \(\frac{16800\times100}{70} = 24000J\)
A plane is inclined at an angle \(\theta\) to the horizontal. Its velocity ratio is
Velocity ratio = \(\frac{Effort distance}{Load distance}\)
On an inclined plane, it is the inverse of \(sin\theta\) = \(\frac{1}{sin\theta}\)
The diagram above illustrates a beaker of water being heated. It is observed that as the bubbles rise they get bigger in size.The reason for this observation is
When a bubble is deep under water, it has both atmospheric pressure and water pressure (giving it depth), acting on it but as it rises, the water pressure decreases. At this point, the basic pressre acting on the bubble is the atmospheric pressure. Recall that pressure is inversely proportional to volume (Boyles' law), hence, the less the pressure, the more the volume.
Which of the following devices converts light energy to electrical energy?
The solar cell converts light from the sun to electricity.
A motor of a corn mill machine operates on electrical energy of \(1.44 \times 10^{5}\)J. If one-quarter of the energy is wasted on sound and heat, determine the efficiency of the machine.
Thermal energy added or removed from a substance that changes the state of the substance is called
Latent heat is thermal energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process.
The maximum density of water occurs at a temperature of
This is as a result of the Hydrogen bonding in water. Due to the high Kinetic Energy of water, the hydrogen bonds can't hold for too long but from 4°C, there's an increase in the hydrogen bonds hence strenghtening it. From the point of production of more hydrogen bonds, the bonding is no longer easily broken. Generally, these and a few factors based on these cause the density of water to be maximum at 4°C.