Take the mechanical equivalent of heat as 4 J/cal.A 10-gram bullet moving at 2000 m/s plunges into 1 kg of paraffin wax (specific heat 0.7 cal/g .°C).The wax was initially at 20°C.Assuming that all the bullet's energy heats the wax, its final temperature is:

Question

Quizplus · Accepted Answer

First, we need to calculate the total energy of the bullet:

Kinetic energy = 0.5 x mass x velocity^2 
Kinetic energy = 0.5 x 0.01 kg x (2000 m/s)^2 
Kinetic energy = 20,000 J

Now we can use the mechanical equivalent of heat to convert this energy into calories:

20,000 J = 4784.7 cal

Next, we can use the specific heat formula to calculate how much the temperature of the wax will rise:

heat absorbed = mass x specific heat x change in temperature

We know the mass is 1 kg and the specific heat is 0.7 cal/g°C. We just need to solve for the change in temperature:

4784.7 cal = 1 kg x 0.7 cal/g°C x (final temperature - 20°C)

Simplifying this equation, we get:

final temperature - 20°C = 6835°C / 1000 
final temperature - 20°C = 6.835°C 
final temperature = 26.835°C

Rounding to the nearest tenth, the final temperature of the wax is 27.1°C. Therefore, the answer is D.

Take the Mechanical Equivalent of Heat as 4 J/cal