What does constant acceleration mean?

ok I just confused myself. does constant acceleration mean that it doesn change or that it changes constantly?

Constant acceleration means that an object has a velocity that keeps changing constantly. The amount of acceleration is the same.

So, if a car had constant acceleration, and it starts moving from a stop (in which case, when stopped it had a velocity of 0) then say at:

1 sec after moving its going 2 miles an hour;
2 sec after moving its going 4 miles an hour;
3 sec after moving its going 6 miles an hour;
4 sec after moving its going 8 miles an hour;
and so on.

So the velocity (the speed of the car, in this case in miles an hour) is constantly changing (its going up)- but the amount of acceleration stays the same, at 2 miles a second, I.e its constant.

Hope that makes sense!

I ll simplyfy it

a particle has a velocity X...
now it is said to have a constant velocity A...
So the velocity of the particle is X+A in the first second and X+A+A in the second second and so on...
just that the addition in velocity is a constant...

Cinthia, The previous examples are correct, however, remember that acceleration is BOTH a velocity AND a direction. (Ignoring air resistance) a ball dropped off a cliff has a constant acceleration due to gravity and will keep falling faster until it hits the ground. ALSO, a race car going exactly 100 MPH on an exactly circular track is also undergoing constant acceleration because its Direction is constantly changing by the same amount.

^^^ In the case of the ball, its acceleration will stop if it reaches terminal velocity however.

bimjob means that acceleration has both magnitude and direction, it is a vector. Mechanics of a moving object is easily understood using Newtons law of physics and algebra where force is the product of mass and acceleration. If the acceleration is constant then there is a constant force acting on the object. This could be a negative force (opposite direction) like air resistance causing any moving object to decelerate and since this force is proportional to velocity then it will not be a constant deceleration. In the case of a falling object the force of gravity is proportional to the mass of the object since gravity is constant acceleration determined by the constant mass of the earth. The object accelerates to the terminal velocity at which point air resistance balances the force of gravity and the object continues with it's momentum (mv) but no further acceleration to the ground.

Extending mechanics to calculus, you will see that the derivative of distance with respect to time is velocity, and the derivative of velocity with respect to time is acceleration, and physicists never calculate the derivative of acceleration but it would calculate as zero when constant as you can imagine if an object had constant velocity would mean zero acceleration which is constant.