Question

A car covers 72 kilometers in the first hour of its journey. In the next hour, it covers 90 kilometers. What is the amount of work done by the car? The total mass of the car, including its passengers, is 2.5 × 103 kilograms.

A. 2.8 × 105 joules
B. 4.0 × 105 joules
C. 5.1 × 105 joules
D. 2.8 × 106 joules
E. 2.8 × 107 joules

Answer 1

(1/2)*2500*(25^2) - (1/2)*2500*(20^2) = 281250 J, which can also be expressed as 2.8 x 10^5 Joules.

Step-by-step explanation:

Answer 2

The amount of work done can be solved using the formula:

Work = Force x Distance = Change in kinetic energy

Kinetic energy can be solved using the formula: KE = (1/2)*m*v^2
So, change in kinetic energy = (1/2)*m*(Vf)^2 - (1/2)*m*(Vo)^2

Where:

Vf = final velocity = 90 kph = 25 m/s
Vo = initial velocity = 72 kph = 20 m/s

substituting the given values:

Work = (1/2)*2500*(25^2) - (1/2)*2500*(20^2) = 281250 J, which can also be expressed as 2.8 x 10^5 Joules.

Among the choices, the correct answer is A.