What is the work done by a car's braking system when it slows the 1500-kg car from an initial speed of 96 km/h down to 56 km/h in a distance of 55 m?
A)8.3 kJ
B)20 kJ
C)1.3 MJ
D)2.5 MJ
E)8.3 MJ

Question

Quizplus · Accepted Answer

The work done by the braking system can be calculated by the formula:

Work = (1/2)mv^2

where m is the mass of the car, v is the velocity of the car. We can use this formula to calculate the initial kinetic energy of the car:

KE1 = (1/2)(1500 kg)(26.67 m/s)^2 = 1.3 MJ

Similarly, we can use the same formula to calculate the final kinetic energy of the car:

KE2 = (1/2)(1500 kg)(15.56 m/s)^2 = 509 kJ

The work done by the braking system is the difference between the initial and final kinetic energies of the car:

Work = KE1 - KE2
     = 1.3 MJ - 509 kJ
     = 791 kJ
     = 0.791 MJ

Therefore, the best choice is C, 1.3 MJ.

What Is the Work Done by a Car's Braking System