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A man has pulled a cart through 35 m applying a force of 300 N. Find the work done by the man. (10500 J)
Solution:
Distance = S = 35 m
Force = F = 300 N
Work done = W = ?
W = $F \times S$
W = $300\times 35$
W = 10500 J
A block weighing 20 N is lifted 6 m vertically upward. Calculate the potential energy stored in it. (120 J)
Solution:
Weight of the block = W = 20 N
Height = h = 6 m
Potential energy = P. E. =?
P.E. = mgh
We know that w = mg
P.E. = $(mg) \times h$
Thus, P.E. = $(2 \times 10)\times 6$
P.E. = 120 J
A car weighing 12 k N has a speed of 20 $ms^{-1}$. Find its kinetic energy. (240 kJ)
Solution:
Weight of the car = w = 12kN = $12\times 1000$ N = 12000 N
Speed of the car = v= 20 $ms^{-1}$
Kinetic energy = K.E. = ?
K.E. = $\frac{1}{2} m v ^{2}$
W = mg or m = $\frac{w}{g}$
m = $\frac{12000}{10}$ = 1200 kg
Thus, K.E. = $\frac{1}{2}\times 1200 \times (20)^{2}$
= $600 \times 400$ = 240000 J
K.E. = 240 kJ
