# Kinetic energy to thermal energy

1. May 15, 2015

### goonking

1. The problem statement, all variables and given/known data

2. Relevant equations

Q = c m ΔT
3. The attempt at a solution
so converting 55 mph to meters per sec gives me a velocity of 24.58 m/s

kinetic energy of car is 1/2 m v2

i set 1/2 m v2 = c m ΔT

plugging in v and c and masses of both

ΔT = 134.56

is that correct?

2. May 15, 2015

### Orodruin

Staff Emeritus
There is a central piece of information missing here: How many brakes does the car have? That is, how many of the car's wheels have brakes.

3. May 15, 2015

### goonking

so there is no way i can answer this question? or do i just assume its 4? 1 for each wheel

4. May 15, 2015

### Orodruin

Staff Emeritus
Unless you are a mind reader, no. I am not very familiar with cars, but I would assume that either all wheels or one pair of wheels would have brakes.

5. May 15, 2015

### Raghav Gupta

So if we choose 4 wheels as it is most common, then has moment of inertia a role here?

6. May 15, 2015

### haruspex

In principle, yes, but we have no information on the moments of inertia of the wheels or their radius. Besides, it would be small compared with the linear KE of the vehicle.