How and why the brakes of a car gets much hotter than brakes of bicycle?

How and why = the increase of temperature of the brakes is due to the friction generated between two surfaces. But for a better understanding let's put some numbers on it, and let's assume some logical conditions.

Explanation:

We can see in the image attached the mass of the biker and the mass of a car, let's assume the biker mass of 90 (Kg) and a vehicle mass of 1000 (kg).

Then suddenly both of them have the need of stop because they want to avoid a possible collision.

Let's suppose that at the moment when they use the breaks the car and the bike are having a displacement of 1 meter. And both stopped in 1,25 seconds

Note. We have to understand that when the breaks are acting, there is a friction force between the tires and the pavement, but there is another friction force between the breaks and the wheel, the last one is the one that we are interested because there is a process of generation and dissipation of heat. This condition is the same for the bike.

Let's assume also a friction coefficient of 0,2.

We can see that there is more energy generated when the breaks of the car are applied because of the larger mass of the vehicle compared with the biker.

b.transmitters send radio waves, and receivers capture radio waves.

false br