Question

3. A 20 kg lawnmower is pushed by its handle, which makes a 40 degree angle with the horizontal. What
work is done by the person pushing the mower if she pushes along the handle with 30 N of force, the lawn is 20
m long, and requires 30 passes to finish?

Answer 1

13788 J is required to finish the work.

Explanation:

Given that,  

Mass of lawnmower is 20 kg  

Force = 30 N

$\text { Angle }(\theta)=40^{\circ}$

Displacement ( distance moved )= 20m

The force of 30N is applied along the direction of motion and was applied for the whole 20 m.

The formula of work done for one pass is

$\text { Work done }=\text { force } \times \text { displacement } \times \cos \theta$

Substituting the given data into the formula,

$W=30 \times 20 \times \cos 40^{\circ}$

$\mathrm{W}=600 \times \cos 40^{\circ}$

$\mathrm{W}=600 \times 0.766$

W = 459.6 J

Work done for one pass = 459.6J

Now, work done for 30 passes is calculated by multiplying the work done for one pass into 30.

$\text { Then the work done for } 30 \text { passes is } 459.61 \times 30=13788 \mathrm{J}$

Work is done by the person pushing the mower to finish the work is 13788 J.