Answer:
Work Done by the Brakes = - 60000 J
Negative sign indicates the opposite direction of force and displacement.
Step-by-step explanation:
Assuming that frictional effects are negligible, we can say that all the work done by the brakes is used to stop the car. We can apply law of conservation of energy to this situation as follows:
Work Done by the Brakes = Change in Kinetic Energy
Work Done by the Brakes = Final Kinetic Energy - Initial Kinetic Energy
Final Kinetic Energy of the roller coaster will be 0. Because, the roller coaster will stop finally and its velocity will become zero.
Work Done by the Brakes = 0 J - 60000 J
Work Done by the Brakes = - 60000 J
Negative sign indicates the opposite direction of force and displacement.