Which of the following surfaces will absorb radiant heat energy?
white
red
black
blue
Correct answer is C
A black solution is a better radiator of heat and allow a better absorber of heat.
Which of the following is a semiconductor
copper
silicon
plastic
Iron
Correct answer is B
Semi-conductor have an elecctric conductivity intermediate in value between that of a pure metal and a good insulator. Silicon is an example
Which of the following is correct about an electric cell?
Primary cell produces a large current for a long time
Secondary cell has a very high internal resistance
Primary cell has a very low internal resistance
Secondary cell has a very low internal resistance
Correct answer is D
About electric cell
Primary cells are used up gradually often the cells are use and it can't be recharged
Secondary cells or accumulated can be recharged and used for a long period of time and their main advantage is that they have low internal resistance
II and III only
I, II and III
I and II only
I and III only
Correct answer is B
Refraction, Interference and diffraction are all properties of waves
125kgms−1
25kgms−1
15kgms−1
0kgms−1
Correct answer is B
Impulse = momentum
Impulse = Force (f) × time (t)
Momentum = mass (m) × velocity (v)
∴ Ft = Final momentum - initial momentum
FT = mv - mu
Since it is initially at rest u = 0
∴ 5 × 5 = mv − m(0)
25 = mv
∴ Final momentum = 25kgms\(^{-1}\)