a student is riding the school bus. the bus stops as the driver applies the brakes. which these statements best describes this situation?
A. the bus is gaining energy because of friction
B. a force is changing the motion of the bus
C. there is no acting on the bus so it stops moving
D. the school bus does not lose or gain kinetic energy
B. a force is changing the motion of the bus
B. a force is changing the motion of the bus
The statement that best describes this situation is B. A force is changing the motion of the bus.
When the school bus stops, the driver applies the brakes, which creates a force that opposes the bus's motion. According to Newton's First Law of Motion, an object will continue in its current state of motion unless acted upon by an external force. In this case, the force from the brakes acts as an external force, causing a change in the motion of the bus and bringing it to a stop.
Option A, "the bus is gaining energy because of friction," is incorrect. Friction between the bus and the road converts the bus's kinetic energy into heat energy, causing it to slow down and eventually stop. It is not gaining energy.
Option C, "there is no acting on the bus, so it stops moving," is also incorrect. As mentioned earlier, the force applied by the brakes acts on the bus, causing it to stop moving.
Option D, "the school bus does not lose or gain kinetic energy," is incorrect. When the bus stops, it loses kinetic energy as it slows down and comes to a complete stop. The energy is converted into other forms, such as heat energy through friction.
Therefore, the correct answer is B. A force is changing the motion of the bus.