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What is the kinetic energy of an object?
The energy possessed by a body by virtue of its motion is termed mechanical energy or kinetic energy. Every moving object possesses mechanical energy. A body uses mechanical energy to try to work. The kinetic energy of the hammer is employed in driving a nail into a log of wood, the mechanical energy of air is employed to run wind mills, etc.
Write an expression for the kinetic energy of an object.
If a body of mass m is moving with a speed v, then its K.E. Ek is given by the expression,
Ek = 1/2 m v2
Its SI unit is Joule (J).
The kinetic energy of an object of mass, m moving with a velocity of 5 ms-1 is 25 J. What will be its kinetic energy when its velocity is doubled? What will be its kinetic energy when its velocity is increased three times?
Given
K.E. of the object = 25J
Velocity of the object (v) = 5 m/s
K.E. = (½) mv2
25 = (½) m (5)2
50 = 25 x m
m = 50/25
m = 2 kg
Now, when velocity is doubled
v = 10 m/s
m = 2 kg
K.E. = (½) x 2 x (10)2
K.E. = 102
K.E. = 100 J
When velocity is increased three times, then
v = 15 m/s
m = 2 kg
K.E. = (½) x 2 x (15)2
K.E. = (15)2
K.E. = 225 J