A 2.7-kg copper block is given an initial speed of 4.0 m/s on a rough horizontal

Question

A 2.7-kg copper block is given an initial speed of 4.0 m/s on a rough horizontal surface. Because of friction, the block finally comes to rest.

(a) If the block absorbs 85% of its initial kinetic energy as internal energy, calculate its increase in temperature.

(b) What happens to the remaining energy?

2. A certain steel railroad rail is 13 yd in length and weighs 80.0 lb/yd. How much thermal energy is required to increase the length of such a rail by 3.0 mm? Note: Assume the steel has the same specific heat as iron.

Explanation / Answer

K.E = ½mV²
K.E = ½(2.3)(2)² = 5.4 J
85% K.E = 0.85x5.4 = 4.59 J


Q = mcT
c of copper = 390

4.59 = 2.7 x 390 T
T = 4.358974359x10^-3° C

2.Equations you will need:

L/L = T
Q = mcT

T = ? degrees

Q = mcT = ? J

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