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

Acceleration=
`0.5m/s^2`

Speed=0.67 m/s

Step-by-step explanation:

We are given that

Horizontal force=F=20 N

Mass of box=m=40 kg

We know that

Acceleration=
`a=(F)/(m)`

Using the formula

Acceleration of box=
`(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=(30)/(40)=(3)/(4) ms^(-2)`

`v^2-u^2=2as`

Substitute the values

`v^2-0=2* (3)/(4)* 0.3=0.45`

`v^2=0.45`

`v=√(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