Question

A car of mass 750 kg accelerates away from traffic lights. At the end of the first 100 m it has reached a speed
of 12 m/s. During this time, its engine provides an average forward force of 780 N, and the average force of
friction on the car is 240 N.
a Calculate the work done on the car by the force of its engine.
b Calculate the work done on the car by the force of friction.
c Using ke. = mv2, calculate the increase in the car's kinetic energy at the end of the first 100 m.
d Explain whether your answers are consistent with the principle of conservation of energy.​

Answer 1

Answer:

a. 78, 000J or 78kJ

b. 24, 000J or 24kJ

c. 54, 000J or 54kJ

Explanation:

a. workdone = force x distance. engines force= 780N so,

780N x 100m = 78, 000J

b. workdone = force x distance. frictions force= 240N so,

240N x 100m = 24, 000J

c. kinetic energy= 1\2 x m x v2

= 1\2 x 750kg x 12 squared = 375 x 144=  54, 000J