- #1

- 36

- 1

## Homework Statement

A crane lifts a load of 3000 kg to a height of 8.5 meters in 15 seconds.

Calculate the lift work?

## Homework Equations

## The Attempt at a Solution

This is a very simple problem but the thing is its unclear data. The given data does not clarify whether or not this is an accelerated motion. So there will be two ways to solve it.[/B]

**1. The first solution**

Assuming that this is a uniform motion.

**F=P=m.g**

A= F.s = m.g.h= 3000.(9.81).(8.5)= 250,155 J

A= F.s = m.g.h

**2.The second solution**

Assuming that this is an accelerated motion

**F-P = m.a → F= (a+g)m**

**a= 2h/t**= 2.(8.5)/15

^{2}^{2}≈ 0.076 m/s

^{2}

→F= (0.076+9.81).3000=29658 N →

**A=F.s**=29658.(8.5)= 252,093 J

I want to ask you that how can we know whether or not this is an accelerated motion so that we have only one solution. Thanks