Physics 2020 JAMB Past Questions - Question 1: A car of mass 800kg attains a speed of 25m/s in 20 secs. The power developed in the engine is

Correct Answer

B

Explanation

power = force X distance/time = m(v-u/t) X V = 800 (25-0)/20 X 25 = 2.5 X 10� wattsTo calculate the power developed by the engine, we can use the formula:

\[ \text{Power} = \text{Force} \times \text{Velocity} \]

First, we need to find the force acting on the car. We can use Newton's second law, which states that force is equal to mass times acceleration (\( F = ma \)).

The acceleration of the car can be found using the equation:

\[ a = \frac{\text{change in velocity}}{\text{time}} \]

Given that the car attains a speed of 25 m/s in 20 seconds, the change in velocity is 25 m/s and the time is 20 seconds. Therefore, the acceleration is:

\[ a = \frac{25 \, \text{m/s}}{20 \, \text{s}} = 1.25 \, \text{m/s}^2 \]

Now, we can find the force acting on the car:

\[ F = ma = 800 \, \text{kg} \times 1.25 \, \text{m/s}^2 = 1000 \, \text{N} \]

Finally, we can calculate the power developed by the engine using the force and velocity:

\[ \text{Power} = \text{Force} \times \text{Velocity} = 1000 \, \text{N} \times 25 \, \text{m/s} = 25000 \, \text{W} \]

So, the power developed by the engine is 25000 watts.