A car is moving at a speed of 50 km/hour. The driver takes her foot off of the accelerator and the car coasts to a stop. Why?

A)
No acceleration means no movement.

B)
Energy is no longer being transformed.

C)
Without an external energy source, friction stops the car.

D)
All the kinetic energy is converted to potential energy or energy of position.

Question

A car is moving at a speed of 50 km/hour. The driver takes her foot off of the accelerator and the car coasts to a stop. Why?
	

A)
	No acceleration means no movement. 	
	

B)
	Energy is no longer being transformed. 	
	

C)
	Without an external energy source, friction stops the car. 	
	

D)
	All the kinetic energy is converted to potential energy or energy of position.

abhisar · Answer

What do you think it should be?

anonymous · Answer

the answer is C) Without an external energy source, friction stops the car.  Reason: according to NEWTON'S Ist LAW OF MOTION a body will continue to be in its state of rest or motion until and unless an external force is applied on it. In this case friction acts as an external force and stops the car as it is acting to oppose the motion of the car.