Question

A crane exerts a power of 11kW on an object which travels upwards for 4 seconds. The mass of the object is 100kg. The body has an acceleration of 0.1m/s². What height is the body on, and what height is the body on if the utility  η=60%

Answer 1

Given:

The power exerted by the crane is P = 11kW = 11000 W.

The time is t = 4 s.

The mass of the object is m = 100 kg.

The acceleration of the object is a = 0.1 m/s^2.

To find the height of the body, h.

Step-by-step explanation:

The height of the body can be calculated by the formula

`\begin{gathered} P=\text{ }(force* displacement)/(time) \\ =(ma-mg* h)/(t) \\ h=(Pt)/(ma-mg) \end{gathered}`

On substituting the values, the height will be

`\begin{gathered} h\text{ =}(11000*4)/((100*0.1)-(100*9.8)) \\ =-45.36\text{ m} \end{gathered}`

Here, the negative sign indicates that the object is moving upwards.