Work– When ever a force makes a body move , then work is said to be done.
So , The work done by a force on a body depends on two factors
So mathematically we can write Work done = Force X Distance
Unit of Work As W = F X D = N.m = Joule
Therefore unit of work done is Joule .
Again Let me write the definition for the same
Work done is defined as product of the force and the distance over which the force is applied
The SI unit of work is the joule (J), which is defined as the work expended by a force of one newton through a displacement of one meter.
W= work done
m= mass of the body
g= acceleration due to gravity
h= height through which the body is lifted
We always advise try to solve by your own . at first . then look for the solutions.
The work done is calculated s W = F X S ( Force X Distance)
F= 20 N
Distance = s = 1 metere
Work done = 10 * 1 = 10 Joule
2. Calculate the work done in lifting 150 kg of water through a vertical height of 10 metere. 9 Assume g = 10 m/s2)
As we are lifting the water . so the work is done against gravity .
Hence work = M X g X h ( mass X Acceleration due to gravity X height)
M = 150 Kg
h = 10 Metre
g = 10 m/s2
W= 150 X 10 X 10 = 1500 Joule
A Bus has a weight of 2000kg and travelling at a speed of 60m/s stops after travelling 50 meter when the brakes are applied .
What is the force exerted on it by the brakes.
What is the work done by the brakes
In Order to calculate the force ,first we need to find the acceleration(Actually Retardation) first.
Initial Velocity , u = 60 m/s
Final Velocity, v =0 m/s ( As it is stopped at the end)
Distance traveled = 50 metre
recall = v2=u2+2as
a = -36m/s2
Now Force Applied = m x a = 2000 X 36 = -72000 N
So Force exerted by the brakes on the bus is 72000 newton
work done = Force X Distance
= 72000 X 50 =3600000 Joule = 3.6 X 106 Joule
A porter lifts a luggage of 15 kg from the ground and puts it on his head 1.5 m above the ground. Calculate the work done by him on the luggage
Mass of luggage, m = 15 kg
displacement,s = 1.5 m Work done, W = F × s = mg × s
= 15 kg × 10 m s-2× 1.5 m
= 225 kg m s-2 m
= 225 N m = 225 J
Work done is 225 J
A child pulls a toy car through a distance of 15 metre at an angle of 600 with the horizontal surface . find the work done if the child applies a force of 10 N.
w= Fs Cosθ
Force = 10 N
Angle θ = 600
Distnace s = 15 metre
W = 10 X 15 X Cos 600
= 10 X 15 X 1/2 = 75 Joule
When the force acts perpendicular to the direction of motion or at 90 degree the the work done becomes 0.
w= Fs Cosθ
θ = 900
Cos 90 = 0
So w= 0