A car with a mass of 1,200 kg traveling westward at 30 m/s is
slowed to a stop in a distance of 50 m by the car's brakes.
What was the braking force?

A. 10,800 N
B. 36.000 N
C. 6000 N
D. 9000 N

F = 10800 N

Explanation:

We have,

Mass of a car, m = 1200 kg

Initial speed of the car, u = 30 m/s

Finally speed, v = 0 (as it stops)

Stopping distance, d = 50 m

It is required to find the braking force. For this firstly we can find the acceleration of the car using equation of kinematics as :

Braking force is, F = ma

So, the braking force is 10800 N. The correct option is A

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.