A car is strapped to a rocket (combined mass = 661 kg), and its kinetic energy is 66,120 J.

At this time, the rocket runs out of fuel and turns off, and the car deploys a parachute to slow down, and the parachute performs 36,733 J of work on the car.

What is the final speed of the car after this work is performed?

9.4 m/s

Explanation:

According to the work-energy theorem, the work done on the car is equal to its variation in kinetic energy, so:

where in this problem:

W = -36,733 J is the work done on the car (negative because the car is slowing down)

is the final kinetic energy of the car

is its initial kinetic energy

Solving for Kf,

Now we can find the final speed of the car by writing the formula for the kinetic energy:

where:

m = 661 kg is the mass of the car

v is the final speed

K = 29,387 J is the kinetic energy

Solving for v,

it's