NUMERICAL QUESTIONS
1:- A force of 8 N causes a displacement of 4 m in a body in the direction of force. Calculate the work done.
2:- How much force is applied on a body when 200 joules of work is done in displacing the body through a distance of 5m.
3:- A body of 2 kg is raised to 5m.Find the work done.(g=10m/s2)
(Hint:- Here, Work done=Gravitional potential energy; Work=PE=mgh).
4:- A body of mass 0.5kg is moving with a speed of 20m/s. Find the kinetic energy.
5:- A moving body of mass 0.3kg has 60J of kinetic energy. Calculate the speed of the body.
6:- A machine does 384 J of work in 2 minutes. What is the power of the machine.
(Hint:- a:- Convert 2 min into sec.
b:-( use the formula, P= W/T)
Answers
Answer:
1. 32J 2. 40 N 3. 100 J 4. 100J 5. 20 m/s 6. 3.2 watt
Answer:
1) F(force) = 8N
S(displacement) = 4m
∴ Work done = F*S => (8*4)J = 32 joules(J).
2) Work done = 200J
S = 5m
We know, Work done = F*S
∴ F = Work done / S => (200/5)N = 40N.
3) Weight = 2kg
∴ F = (2*10) = 20N [ Because 1kg = 10N]
∴ Work done = F*S => (20*5)J = 100J.
4) Mass = 0.5kg
velocity = 20m/s
Kinetic energy = 1/2 mv^2 => 1/2 *0.5*20^2 = 1/2 * 5/10 * 20 * 20 = 100J.
5) Mass = 0.3kg
Kinetic energy = 60J
We know, kinetic energy = 1/2 mv^2
∴ velocity or speed square root of 2*kinetic energy * m
=> square root( 2*60*0.3) => square root ( 36) = 6m/s.
6) Work done = 384 J
Time = 2 minutes => 120 seconds [always convert it to seconds]
Power = work done/ΔT [where, ΔT = elapsed time]
=> (384/120) watt(W) = 3.2W.
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