An electric vehicle starts from rest and accelerates at a rate a1 in a straight line until it reaches a speed of v. the vehicle then slows at a constant rate a2 until it stops. (a) how much time elapses from start to stop? (b) how far does the vehicle move from start to stop? give your answers in terms of the given variables.

(a)

In the first part of the motion, the car accelerates at rate , so the final velocity after a time t is:

Since it starts from rest,

u = 0

So the previous equation is

So the time taken for this part of the motion is

(1)

In the second part of the motion, the car decelerates at rate , until it reaches a final velocity of v2 = 0. The equation for the velocity is now

where v is the final velocity of the first part of the motion.

Re-arranging the equation,

(2)

So the total time taken for the trip is

(b)

In the first part of the motion, the distance travelled by the car is

Substituting u = 0 and (1), we find

In the second part of the motion, the distance travelled is

Substituting (2), we find

So the total distance travelled is

answer: option c. i.e. electric current flowing “downhill” from the negative electrode to the positive electrode in a battery

explanation:

the water analogy to the circuits define the pipes (water flows) to the electric current. now, we know that the electric current flows from the positive terminal to the circuit (as shown in the diagram attached).

hence, option c is the correct answer.