when does the ball reach maximum velocity?

[pushing_wins]

does the ball start to decelerate the moment it leaves the string?

or does it require time to accelerate to maximum velocity coming off the strings?

 

[mucat]

does the ball start to decelerate the moment it leaves the string?

or does it require time to accelerate to maximum velocity coming off the strings?

Decelerate the moment it leaves the string.

Someone failed physics I see...

 

[Mountainman]

does the ball start to decelerate the moment it leaves the string?

or does it require time to accelerate to maximum velocity coming off the strings?

I do not think so for the first question. your second hypothesis sounds right.

 

[kevhen]

A very slow ball hit with lots of topspin, could possibly accelerate after it bounced but generally a ball is at maximum velocity as it leaves the strings.

 

[shindemac]

There's no acceleration after the bounce. It's just an illusion because it is faster than we expect. And yes, the fastest point is at contact and it slows down after that. Roughly half the pace by the time it reaches the returner.

 

[deluxe]

does the ball start to decelerate the moment it leaves the string?

or does it require time to accelerate to maximum velocity coming off the strings?

Could happen if you're playing in a tail wind faster than your groundies...

 

[kevhen]

If you put enough topspin on the ball but hit it at a very slow pace, it will accelerate on the bounce. Nobody hits their topspin shots that slow though or with that much spin but it's theoritically possible. Their is extra energy in the ball due the spin.

 

[MTChong]

If you put enough topspin on the ball but hit it at a very slow pace, it will accelerate on the bounce. Nobody hits their topspin shots that slow though or with that much spin but it's theoritically possible. Their is extra energy in the ball due the spin.

Well for that topspin, the ball would have to be very loopy; so I'm sure that though the horizontal velocity may be greater, the overall velocity vector will be less. Is that right?

Anyways, in general cases, you don't accelerate after the initial push.

 

[kevhen]

Also if the surface is smooth and fast but grippy enough to absorb the spin, then the ball has more of a chance to accelerate forward on the bounce. A rough surface will make it more difficult and slow the ball down too much on contact with the ground. A slow kick serve with heavy spin might acclerate slightly on the bounce too.

 

[MTChong]

Also if the surface is smooth and fast but grippy enough to absorb the spin, then the ball has more of a chance to accelerate forward on the bounce. A rough surface will make it more difficult and slow the ball down too much on contact with the ground. A slow kick serve with heavy spin might acclerate slightly on the bounce too.

That sounds about right - it'll accelerate in the horizontal dimension only, I think. (Though I'm not too sure about things like spin as I've only taken AP Physics B which is a useful yet impractical class at the same time. No wind resistance? What's that!)

 

[mucat]

While topspin can help the ball to "move forward" after the bounce, the ball does lose almost half of the speed after the bounce. I don't think anyone can generate enough topspin to compensate for the lost of almost half of the original speed.

Also, the ball has to lost energy after it leaves the racket. I think topspin in the air is just changing the direction of the ball (from forward to downward), topspin in the air doesn't make the ball goes faster.

 

[maverick1]

Well for that topspin, the ball would have to be very loopy; so I'm sure that though the horizontal velocity may be greater, the overall velocity vector will be less. Is that right?

Not necessarily. Try this at home: drop a ball vertically on to the floor from a height of a few inches, with as much spin(about a horizontal axis) as you can impart. Just before it hits the floor, the velocity of the center of the ball will be small(in any direction). But once it bounces, the spin will cause it to move in a horzontal direction with significant speed.

 

[kevhen]

Maverick has it right with an extreme example.

A real life example might be hitting a kick serve at 20 miles per hour with it landing at about 15 mph and then kicking forward back to about 20 mph and then slowing down to 15 mph again by the time the returner hits the return.

I guess the question to answer is how much pace can a good topspin kick add to a ball after the bounce and whether that is greater than how much the ball slows down from the server's racquet to where it strikes the ground. You would need to hit a slow loopy shot to make this possible since the ball does slow down very quickly due to wind resistance.

 

[Hondasteve]

In answer to the OP, the millisecond it comes off of the strings. That is the fastest it will be travelling until it comes to rest or is acted upon by another force.

 

[papa]

Well, maybe this is possible but highly unlikely. I surpose that if you impart enough spin to a ball (like a top) and the ball then strikes the surface (like the top falling over and taking off), then its possible. In other words the energy is stored up in the ball spining, when struck, rather than being used up in traveling forward.

However, in tennis, I don't think this a likely possiblilty. A ball served loses about half its speed by the time it gets to the receiver - maybe not quite half but close. So a ball leaving a racquet at say 100 mph will be going 55-60 mph when it gets to the receiver.

Actually, a rather interesting question. When you first read it you have one thought (of course it slows down) and then the more you think about it you start to explore the extremes.

 

[kevhen]

That other force is the ground and the spin of the ball which creates another force as the ball pushes against the ground and accelerates from it with enough spin on the ball.

Spin is a major part of the game on the men's side from 4.5 level on up.

 

[papa]

That other force is the ground and the spin of the ball which creates another force as the ball pushes against the ground and accelerates from it with enough spin on the ball.

Spin is a major part of the game on the men's side from 4.5 level on up.

Well, the only force associated with the ground is gravity (32 ft/sec) which does effect the downward speed of a ball.

I think your talking about the "top" (like toy top) spining in place and when it falls over, it moves quickly from the point it was spining. In other words while the toy top is spining in place its not moving (generally) from a specific spot.

In theory, this might be possible to some extent anyway with a tennis ball but we're getting pretty far out on a branch here. However, if a ball is indeed hit rather high with a lot of spin, then the speed (toward a particular spot) could be faster after it bounces.