A person sitting in an open car moving at constant velocity throws a ball vertically into the air, the balls falls ____________

Friction is a force that opposes the relative motion of two surfaces in contact. It can slow down and stop stationary objects from moving.  Friction is proportional to the normal force exerted between the surfaces. It does not depend on the area of contact, but it does depend on the type of surfaces in contact.  Friction can also cause motion. For example, static friction helps us get a grip with the ground to push against the ground in order to move forwards. Kinetic friction acts as a driving force when it comes to motion of a wheel.  Here are some other facts about friction: The... Show more

Friction is a force that opposes the relative motion of two surfaces in contact. It can slow down and stop stationary objects from moving. 
Friction is proportional to the normal force exerted between the surfaces. It does not depend on the area of contact, but it does depend on the type of surfaces in contact. 
Friction can also cause motion. For example, static friction helps us get a grip with the ground to push against the ground in order to move forwards. Kinetic friction acts as a driving force when it comes to motion of a wheel. 

Here are some other facts about friction:
The coefficient of static friction is greater than the coefficient of kinetic friction.
Limiting friction is the maximum value of friction up to which the body does not move.
In a frictionless world, more objects would be sliding about, clothes and shoes would be difficult to keep on and it would be very difficult for people or cars to get moving or change direction. 

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