N1 Engineering Science|The Easy Way! 61 Example 3.2


A horizontal force of 230 N is required to pull a trolley 30 m, at constant speed, across a horizontal surface in 40 s. Determine; (a) (b) (c) (d)


the work done,


the speed of the trolley, the power required, and


the time it would take to cover a distance of 135mat the same speed. Solution:


Given: F = 230 N (a) W= ? s = 30m t = 40 s


(b) v = ?


(c) P = ? (d)


(a) W = F × s


= 230 × 30 = 6 900 J = 6,9 kJ


(c) P = F × v


= 230 × 0,75 = 172,5W


(d) \ t = s


v = s v


t = 135 or = 180 075,


t = 180 s 60


= 3 minutes Example 3.3


The power required to tow a trailer at a constant speed of 90 km/h on a level road is 35 kW. Determine; (a) (b) (c) (d)


the speed of the trailer in m/s, the force in the towbar,


the work done in 2,5 minutes, and the distance covered in 2,5 minutes.


or t = ? (b)


s = 135m v = s


t = 30 40 = 0,75 m/s P = Fs


× t


= 230 30 = 172,5W


40 ×


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