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A box weighing 25 N is lifted to a height of 1.1 m by sliding it up a ramp 3.2 m long. The person pushing the box exerts a force of 9.9 N.

What is the mechanical advantage of the ramp?

b. What is the machine's efficiency?

5. What is the power of a crane that lifts a 120 N load 14 m in 3.6 s?

1 Answer

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Answer:

a. The mechanical advantage of the ramp is:

Mechanical advantage = length of ramp / height

Mechanical advantage = 3.2 m / 1.1 m

Mechanical advantage = 2.91

b. The efficiency of the machine is the ratio of output work to input work, expressed as a percentage. In this case, the output work is the work done on the box (force x distance), which is:

Output work = force x distance

Output work = 25 N x 1.1 m

Output work = 27.5 J

The input work is the work done by the person pushing the box, which is:

Input work = force x distance

Input work = 9.9 N x 3.2 m

Input work = 31.68 J

The efficiency of the machine is:

Efficiency = (output work / input work) x 100%

Efficiency = (27.5 J / 31.68 J) x 100%

Efficiency = 86.8%

Therefore, the efficiency of the machine is 86.8%.

c. The power of the crane is given by the formula:

Power = work / time

where work is the product of force and distance, and time is the duration over which the work is done.

In this case, the work done by the crane is:

Work = force x distance

Work = 120 N x 14 m

Work = 1680 J

The time taken to lift the load is 3.6 s. Therefore, the power of the crane is:

Power = work / time

Power = 1680 J / 3.6 s

Power = 466.7 W

Therefore, the power of the crane is 466.7 watts.

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