Physics Q thats bugging me

runawaytrain

Hi just wondering, if a ball is thrown, when it reachs its heighest point is its acceleration zero?

Any Responces appreciated

Thanks

Grudaire

runawaytrain wrote: »

Hi just wondering, if a ball is thrown, when it reachs its heighest point is its acceleration zero?

Any Responces appreciated

Thanks

No

It's vertical SPEED is zero at it's highest point - it's acceleration will never be zero (gravity) unless it's being held.

cooperguy

As far as im aware there has to be a split second where the ball is not going up any more and hasnt started coming down yet when its acceleration is zero. It cant go from +1metre/second to -1m/s without passing 0m/s!!

Thomas_S_Hunterson

cooperguy wrote: »

It cant go from +1metre/second to -1m/s without passing 0m/s!!

You're talking about speed here. At the apex of its flight, it's speed is zero.

Acceleration is measured in metres per second squared. All through its flight, it's vertical acceleration is ~9.81 m/s^2

ApeXaviour

Sean K is right. To expand on what he said. The moment it leaves your hand it stops accelerating upwards (let's call it positive direction) since there is no upward force on it, and begins accelerating downward (negative direction) as gravity is the only force left acting upon it (not counting air resistance, buoyancy etc.).

So when it leaves your hand it accelerates at a constant -9.81m/s/s, reducing it's vertical velocity, eventually turning it negative, until it hits the ground.

Hope that helped

CathalMc

And a graph to see whats going on more intuitively.

If you eyeball it, the slope of the position is velocity, the slope of the velocity is acceleration. So acceleration can never be zero.

amen

surely your acceleration graph is incorrect?
once the ball has reached is apex and is coming back towards to ground its acceleration is once again 9.81m/s/s?

and why would the acceleration not be zero at the apex of its flight if even for for just a split second?

Thomas_S_Hunterson

amen wrote: »

and why would the acceleration not be zero at the apex of its flight if even for for just a split second?

Acceleration is the rate of change in speed.

If acceleration was zero, the speed would be constant. The speed is however changing at a constant rate of ~9.81 m/s^2

EL_Loco

the force of gravity acting on it is constant, it's speed changes but not it's acceleration, acceleration can be negative, which it is in this case, slowing the balls rise, and then bring it downwards.

the fact it stops a one point doesn't halt the "pull" on the ball. You've just picked the point when the ball stops moving, has "run out" of vertical lift and is going in the other direction.

amen

yes but at the point you are infact experiencing a slight moment of zero acceleartion.

Grudaire

amen wrote: »

yes but at the point you are infact experiencing a slight moment of zero acceleartion.

No.

If it experiences zero acceleration it'll keep doing whatever it is doing. ie keep the same velocity

t-ha

amen, might be time to quit physics...