Advertisements
Advertisements
Question
Calculate the decrease in the kinetic energy of a moving body if its velocity reduces to half of the initial velocity.
Advertisements
Solution
We know for kinetic energy, body must have velocity
Let initial velocity = v
Also, Kinetic energy is equal to
K.E. = `1/2"m""v"^2`
given velocity decreased to half, so new velocity v'
v' = `"v"/2`
= K.Enew = `1/2 "m" xx ("v"/2)2`
= K.Enew = `1/2 "m" "v"^2/4`
∴ K.Enew = `("m""v"^2)/8`
Now, as asked, we need to find the decrease
Δ K.E = `("m""v"^2)/2 - ("m""v"^2)/8`
Δ K.E = `3/4"m""v"^2`
Kinetic energy will decrease by `3/4`th of initial kinetic energy.
RELATED QUESTIONS
Write true or false of the following statement.
There is always some loss of energy in conversion from one form of energy to another form, so the total energy is not conserved.
State two factors on which the kinetic energy of a moving body depends.
A cyclist doubles his speed. How will his kinetic energy change: increase, decrease or remain same ?
Name the type of energy (kinetic or potential) possessed by the following:
A moving bus.
Name the two groups in which various sources of energy are classified. State on what basis are they classified.
A hydroelectric power station takes its water from a lake whose water level is 50 m above the turbine. Assuming an overall efficiency of 40%, calculate the mass of water which must flow through the turbine each second to produce power output of 1 MW. (Take g = 10 m s−2).
A metal ball of mass 2kg is allowed to fall freely from rest from a height of 5m above the ground.
What the kinetic energy of the ball just before it hits the ground ?
What happens to the K.E. when
(i) the mass of the body is doubled at a constant velocity and
(ii) the velocity of the body is doubled at constant mass?
Name a device in which solar energy is converted into electricity state its two uses.
State two advantages and disadvantages of using nuclear energy for producing electricity.
