Acceleration of a Projectile?

what will happen if the acceleration is zero at the highest point of a projectile?
- ronica (age 18)
india

One of Newton's Laws is that the acceleration of a body is proportional to the force acting on the body divided by its mass.   For a projectile with no additional propulsion the forces are those of gravity and air resistance.  Neglecting air resistance for the moment, the remaining force is that of gravity which is always g and directed downward.  So the acceleration at the highest point is the same as at launch time, i.e. -9.8 meters/sec² in the vertical direction.  If you want to add in the air resistance force at the apogee it would be against the horizontal component of the velocity.

So to answer your question: the acceleration is never zero, except when it falls back to earth and sticks in the ground.
 
LeeH  

(published on 07/16/2010)