How high can a 21 watt motor lift a 10kg package in 6 seconds?

Answer: 1.3 m

Explanation:

Given that,

power of motor lift = 21 watts

Mass of package (m) = 10 kg

height (h) = ?

Time (h) = 6 seconds

Since power is the rate of work done per unit time i. e Power is simply obtained by dividing work by time. Its unit is watts.

i. e Power = work / time

[since work = force x distance,

& force = mass x acceleration due to gravity (g) ]

Then, Power = (mass x acceleration due to gravity x height) / time

Recall that g has a value of 9.8 m/s²

I. e Power = mgh / t

21 watts = (10 kg x 9.8 m/s² x h) / 6s

21 watts = (98 kgm/s² x h) / 6s

Cross multiply

21 watts x 6s = 98 kgm/s² x h

126 watts•s = 98 kgm/s²•h

Divide both sides by 98 kgm/s²

126 watts•s / 98 kgm/s² = 98 kgm/s²•h / 98 kgm/s²

1.286 m = h

(Round the 1.286 m to the nearest tenth as 1.3 m)

Thus, the package can go 1.3 metres high