## A slice causes a tennisball to spin and deviate from its normal parabolic path.

A tennis player slices the ball to spin and deviate from its normal parabolic path. What is an explanation for this phenomenon?

I am having trouble visualizing the phenomena that is occurring with the slice.
Is the velocity changing on the object and if so, in which direction is it changing?
Is the acceleration changing and if so, in which direction is it changing?

Somebody told me that it was due to some magnus effect in which bernoulli's principle was applied. This principle created a increase of pressure on one side (which I don't know if it's the top side of the ball or down side of the ball) and a decrease in pressure on the other side.
And that this created less of a downward acceleration.

I can't visualize this magnus effect as well as I don't know how it changes the acceleration due to gravity. I also don't know how this changes the path the tennis ball would take.

I watched videos of slicing on youtube, it did not help lol.
Thanks!
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 Spinning the ball doesn't change the acceleration due to gravity, it simply creates extra forces on the ball due to the motion of the air around it.
 What are these forces, and what direction might these forces, or force be pointing in relative to the downward -9.80m/s^2 acceleration. Lastly, does this force have a uniform acceleration? Thanks matterwave

Mentor

## A slice causes a tennisball to spin and deviate from its normal parabolic path.

It is an aerodynamic force from the air flow. The pressure is different on the top and the bottom, this gives an acceleration upwards/downwards (depending on the direction of rotation) or even sidewards with sidewards rotation (didn't see that yet in tennis, but it is important in table tennis).

The total acceleration of the ball is the sum of gravity (9.81m/s^2 downwards), air drag (against the direction of motion) and magnus effect (sidewards, depending on the direction of rotation).