Classify the following situations into contact and non-contact forces. (a) Applying brakes in a vehicle
(b) a coconut falling from a coconut tree
(c ) the planets revolving around the sun
(d) a ball is rolling on ground.

(a) Applying brakes in a vehicle - Contact force

(b) a coconut falling from a coconut tree - Contact force

(c ) the planets revolving around the sun - Non-Contact force

(d) a ball is rolling on ground - Contact force

Explanation:

Contact forces are defined as the forces that apply between two objects which are in physical contacts with each other while non-contact forces forces that act between two objects that are not in physical contact with each other.

Given are some of the examples of contact and non-contact forces. So example of contact forces are applying brakes in a vehicle, a coconut falling from a coconut tree and a ball is rolling on ground.

Example of non-contact force is the planets revolving around the sun.

what is the speed of a softball that travels 20m in 2secs

speed = 20/2 = 10 m/s

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.