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 ?

Acceleration=

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=

Using the formula

Acceleration of box=

The acceleration of the box=

Initial velocity=u=0

Force=F=30 N

Distance=s=0.3 m

Substitute the values

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

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form