Aperson is able to pull a rope with a force of 700 n. what is the minimum number of fixed and moveable pulleys that the person will require to lift up a 27,800 n elephant? assume the pulleys themselves are weightless and the system has 100% efficiency. a. 10 fixed, 10 moveable b. 15 fixed, 15 moveable c. 20 fixed, 20 moveable d. 30 fixed, 30 moveable

C. 20fixed, 20moveables

Explanation:

Efficiency of a machine = MA/VR × 100%

MA is the mechanical advantage

VR is the velocity ratio of the pulley

MA = Load/Effort

MA = 27,800N/700N

MA = 39.71

The velocity ratio formula depends on the type of machine. Since the machine in question is a block and tackle system, the velocity ratio will be the number of pulleys in the system.

Using the efficiency formula to get the VR

100 = 39.71/VR × 100

39.71/VR = 1

VR = 39.71

VR = 40(approximately)

This means that the minimum number of pulleys that the person will require to lift the load is 40pulleys i.e 20fixed, 20moveables

total distance travelled = 60 miles

total time taken =1.5 hours

average speed = total distance / total time

60 / 1.5

= 40

therefore, average speed = 40 m/h

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unbalanced force

explanation: