Physics Homework Help?

Question

If a 1300 kg car can accelerate from 35 km/h to 65 km/h in 4.3 s, how long will it take to accelerate from 65 km/h to 95 km/h?  Assume the power stays the same, and neglect friction losses.

Answer 1

Step 1:

Mass of the car is  kg.

Car accelerates from 35 kmph to 65 kmph in 4.3 sec.

Kinetic energy of the car is .

Resultant kinetic energy required to accelerates from 35 kmph to 65 kmph:

.

Power is rate of energy with respect to time.

Substitute and .

.

Power generated by the force that accelerates from 35 kmph to 65 kmph is 34991.4 J/sec.

Step 2:

Find the time when car accelerates from 65 kmph to 95 kmph.

Resultant kinetic energy required to accelerates from 65 kmph to 95 kmph:

Let the time taken by the car to accelerates from 65kmph to 95 kmph as  sec.

Power generated by the force that accelerates from 65kmph to 95 kmph is

Power generated by the force that accelerates from 65kmph to 95 kmph is J/sec.

Power remains same in both cases.

From equation (1) and (2):

Therefore, time taken by the car to accelerates from 65kmph to 95 kmph is  sec.

Solution:

Time taken by the car to accelerates from 65kmph to 95 kmph is  sec.