Question

A car is traveling at 120 kilometers per hour with 35,000 joules of kinetic energy on the freeway when it suddenly applies its brakes and comes to a screeching stop. How much of the original 35,000 joules of energy is left?

Answer 1

0 J is left (No amount of the original 35000 J energy is left)

Step-by-step explanation:

From the question

Kinetic Energy (K.E) = 1/2mv²................... Equation 1

Where m = mass of the car, v = velocity of the car.

make m the subject of the equation.

m = 2K.E/v²..................... Equation 2

Given: K.E = 35000 Joules, v = 120 km/h = (120×3600/1000) = 432 m/s

Substitute these values into equation 2

m = (2×35000)/432²

m = 0.375 kg.

If a brake is suddenly apply,

Then, the velocity of the car = 0 m/s.

Therefore,

K.E = 1/2(0.375×0²)

K.E = 0 J.

From the baove analysis, No amount of the original 35000 J energy is left.