Physics

Problem

The engine of a small lift performs work on the cabin in the following manner: •

t = 0\,\text{s}

t = 2\,\text{s}

: work rises uniformly from

0\,\text{J}

80\,\text{J}

. •

t = 2\,\text{s}

t = 4\,\text{s}

: work rises uniformly from

80\,\text{J}

160\,\text{J}

. •

t = 4\,\text{s}

t = 5\,\text{s}

: work remains constant at

160\,\text{J}

. •

t = 5\,\text{s}

t = 7\,\text{s}

: work decreases uniformly to

120\,\text{J}

. Based on this data, answer the following. a. (i) Sketch a neat work–time graph for the entire

0

–

7\,\text{s}

period. b. (ii) Calculate the power developed in each of the four time intervals. c. (iii) Determine the average power of the engine for the whole

0

–

7\,\text{s}

duration. d. (iv) Explain, using the graph, why the power is zero during the third interval.