Question

In our first example we will consider a very simple application of Newton’s second law. A worker with spikes on his shoes pulls with a constant horizontal force of magnitude 20 N on a box with mass 40 kg resting on the flat, frictionless surface of a frozen lake. What is the acceleration of the box?
If the box starts from rest and the worker pulls with a force of 30 N , what is the speed of the box after it has been pulled a distance of 0.30 m ?

Answer 1

Answer:

Acceleration=$0.5m/s^2$

Speed=0.67 m/s

Explanation:

We are given that

Horizontal force=F=20 N

Mass of box=m=40 kg

We know that

Acceleration=$a=\frac{F}{m}$

Using the formula

Acceleration of box=$\frac{20}{40}=0.5m/s^2$

The acceleration of the box=$0.5m/s^2$

Initial velocity=u=0

Force=F=30 N

Distance=s=0.3 m

$a=\frac{30}{40}=\frac{3}{4} ms^{-2}$

$v^2-u^2=2as$

Substitute the values

$v^2-0=2\times \frac{3}{4}\times 0.3=0.45$

$v^2=0.45$

$v=\sqrt{0.45}=0.67m/s$

Hence, the speed of the box after it has  been pulled a distance of 0.3 m=0.67 m/s