Fig.19 shows a crane lifting a car of mass 850 kg at constant velocity through a height of 12m in a time of 40s. The crane has a working efficiency of 60%.

Question

i) Calculate the tension in the lifting cable (in N)
ii) Calculate the total input power required by the crane to lift the car (in W)
iii) Suggest and explain many ways the crane can be modified to improve its efficiency

Please show all working out with no abbreviations but full equations used. Please help I’m stuck!

Answer 1

I. F = M*g = 850 * 9.8 = 8330 N. = Tension in the cable.

II. Po = F*d/t = 8330 * 12/40 = 2499 J./s = 2499 Watts. = Power out.

Pin = Po/Eff. = 2499/0.60 = 4165 Watts.
= Input power.

Answer 2

Henry what are the equations you used fully written out in words as the abbreviations used are different in my school so please tell me the full words please

Answer 3

I will give you the meaning of the abbreviations, but you will have to write them into the equations.

F = Force in newtons.

2. M = Mass in kilograms.

3. g = Acceleration due to gravity in m/s^2.

4. d = Distance in meters.

5. J = Joules.

6. s = Time in seconds.

7. Pin = Power input.

8. Eff. = Efficiency.