Question

How long will it take a 400 W engine to lift a 100 N object up to a height of 80 m?

Answer 1

Answer:

20 seconds

Explanation:

We are given;

• Power of the engine as 400 watts
• Force as 100 N
• Distance the object is lifted up as 80 m

We are required to determine the time taken.

• We need to know that power is the rate of work done

Therefore;

• Power = Work done ÷ time

But, work done  = Force × distance

• Therefore; In this case;

Work done = 100 N × 80 m

                  = 8000 Joules

• Since , Power = Work done ÷ time

Then, time = Work done ÷ Power

Thus;

Time = 8000 J ÷ 400 W

       = 20 s

Therefore, the time taken by the engine to lift the object is 20 seconds

Answer 2

Answer:

The time will be 20 seconds

Explanation:

The work is:

W=F*d

where:

F=force[N]

d=distance[m]

W=100*80=8000[J]

The time will be given by:

t= Work/power

where:

work=work done by the force[J]

Power=work done in an interval of time [Watts]

t=8000/400

Analysis of units (J / J/s) = [s]

t=20[s]