Question

A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s. What is the average power delivered by the engine? (1 hp = 746 W) A) 50 hp B) 60 hp C) 70 hp D) 80 hp E) 90 hp

Answer 1

Answer:

power, P = 90 hp

Explanation:

It is given that,

Mass of the car, m = 1500 kg

Initial velocity of car, u = 0

Final velocity of car, v = 25 m/s

Time taken, t = 7 s

We need to find the average power delivered by the engine. Work done divided by total time taken is called power delivered by the engine. It is given by :

$P=\dfrac{W}{t}$

According to work- energy theorem, the change in kinetic energy of the energy is equal to work done i.e.

$W=\Delta E=\dfrac{1}{2}m(v^2-u^2)$

$P=\dfrac{\dfrac{1}{2}m(v^2-u^2)}{t}$

$P=\dfrac{\dfrac{1}{2}\times 1500\ kg\times (25\ m/s)^2}{7\ s}$

P = 66964.28 watts

Since, 1 hp = 746 W

So, P = 89.76 hp

or

P = 90 hp

So, the average power delivered by the engine is 90 hp. Hence, the correct option is (E) " 90 hp".