(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A load of 2,5kN is hoisted by means of a rope and a lifting machine with a rotational frequency of 40r/min and a drum diameter of 700mm.

Calculate the following:

1. The torque

2. The speed of the rope or load in m/s

3. The work done per minute

4. The power required to lift the load

5. The efficiency of the lifting machine if an electric motor of 5kW is required to drive the lifting machine

2. Relevant equations

See below

3. The attempt at a solution

This is my first time posting, so I hope I have got the format right. Here's my attempt at the equations

1. T = F x r

T = 2500N x 0.35m

T = 875Nm

2. V = π x d x N/60

V = π x 0.7m x 40/60

V = 1.465m/s

3. WD = F x s

WD = 2500N x (1.465 x 60)

WD = 2500N x 87.9

WD = 219750 joules

WD = 219.75 kJoules

4. P = F x V

P = 2500N x 1.465m/s

P = 3662.5watts

P = 3.663kWatts

5. Eff = OUT PWR/IN PWR %

Eff = 3662.5w/5000w

Eff = 0.7325

Eff = 73.25%

Those were the answers I got. Please correct me if I am wrong, or just give me some guidance and I can re attempt the questions.

Thanks guys :D

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