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Found in: Page 177

### Physics For Scientists & Engineers

Book edition 9th Edition
Author(s) Raymond A. Serway, John W. Jewett
Pages 1624 pages
ISBN 9781133947271

# The record number of boat lifts, including the boat and its ten crew members, was achieved by Sami Heinonen and Juha Räsänen of Sweden in 2000. They lifted a total mass of 653.2Kg approximately 4 Inches off the ground a total of 24 times. Estimate the total work done by the two men on the boat in this record lift, ignoring the negative work done by the men when they lowered the boat back to the ground.

The total work done by the two men on the boat was 15363.36J.

See the step by step solution

## Step 1: Given data

The total mass of the boat and the crew was

$m=653.2\text{kg}$

Displacement of the boat each time was

$h=4\text{inches}\phantom{\rule{0ex}{0ex}}=4·\left(1\text{inches}×\frac{1\text{m}}{\text{39.3701}\text{inches}}\right)\phantom{\rule{0ex}{0ex}}=0.1\text{m}\phantom{\rule{0ex}{0ex}}$

Number of time the boat was raised = 24

## Step 2: Work done against gravity

Work done to raise a mass m by height h is

w=mgh......................................1

Here g is the acceleration due to gravity of value

g=9.8 m/s2

## Step 3: Determining the work done by to raise the boat

From equation (I), the work done to raise the boat each time was

$W=653.2\text{kg}×9.8{\text{m/s}}^{\text{2}}×0.1\text{m}\phantom{\rule{0ex}{0ex}}=640.14·\left(1\text{kg}·{\text{m}}^{2}{\text{/s}}^{\text{2}}×\frac{1\text{J}}{1\text{kg}·{\text{m}}^{2}{\text{/s}}^{\text{2}}}\right)\phantom{\rule{0ex}{0ex}}=640.14\text{J}\phantom{\rule{0ex}{0ex}}$

Total work done to repeat this 24 times was

${W}_{\text{tot}}=24W\phantom{\rule{0ex}{0ex}}=24×640.14\text{J}\phantom{\rule{0ex}{0ex}}=15363.36\text{J}\phantom{\rule{0ex}{0ex}}$

Thus the total work done was 15363.36J.