A 100   g of iron nail is hit by a 1 . 5   kg hammer striking at a velocity of 60   ms - 1 .…

A 100 g of iron nail is hit by a 1.5 kg hammer striking at a velocity of 60 ms-1. What will be the rise in the temperature of the nail if one fourth of energy of the hammer goes into heating the nail ? [Specific heat capacity of iron =0.42Jg-1C-1]
  1. 16.07°C
  2. 6.75°C
  3. 1600°C
  4. 675°C

Solution

If we heat-up an object, then, the energy is used to either change the temperature of the body or to change the state of the body.
If it changes the temperature, then,

Q = mST
where, Q is the heat given, m is the mass and T is the change in temperature.

We know that a moving object has an energy in the form of kinetic energy, i.e.,
KE=12mv2

When that moving object strikes another object, it loses some energy which changes into the heat energy and this heat energy increases the temperature of the object.
Given a hammer of 1.5 kg is moving with 60 m s-1.
Kinetic energy =12mv2 = 12(1.5) (60)2 = 2700 J
One-fourth of kinetic energy changes into heat energy.
   14(KE) = Heat energy
   14(KE) = m(S)(T)
   14(2700) =(100) (0.42) (T)
   T=16.07°C

Asked in: JEE Main 2022 (24 Jun Shift 2)

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