Posted by **sarsi** on Thursday, September 19, 2013 at 3:11am.

A labour is throwing 12 bricks per min from the ground and these just reach the roof which is 3.3 meters high. ifthe weight of each bricks be 3.75 kg then find the horse power with which the labour is working.

- physics -
**Graham**, Thursday, September 19, 2013 at 3:32am
Power is rate of work.

Work is force times displacement.

Force is weight of each brick under gravity. Measure weight in [kgf] (kilogram-force: the weight of 1[kg] in normal gravity).

The conversion rate to metric horsepower is: 1[hp] = 75 [kgf·m/s]

Use: P = Ws/t

Where:

(1/t) = 12[/min] = 0.2[/s]

s = 3.3[m]

W = 3.75[kgf]

- physics -
**Devron**, Thursday, September 19, 2013 at 3:39am
12 bricks/min*(1min/60s)=0.2bricks/s

m=(3.75kg/brick)

F=mg=(3.75kg/brick)*9.8m/s^2=36.75N/brick

d=3.3m

Since Power=Work/t(s)=F*d/t

Power=(36.75N/brick)*(0.2bricks/s)*(3.3m)=24.3 W

***Bricks cancel leaving (N*m)/s

24.3 W*(1hp/745.70 W)=0.0325 hp

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