B Ball bounce force direction

1. Aug 9, 2016

UMath1

When a ball is bounced against a wall at an angle why is that the wall only applies a normal force perpendicular to the collision location? Shouldn't the force applied by the ball against the wall be along the line at which it travels, at an angle? Then by that logic, by Newton's 3rd Law, shouldn't the wall's force be in the same direction?

2. Aug 9, 2016

Bystander

Ideal or non-ideal collision?

3. Aug 9, 2016

Ideal

4. Aug 9, 2016

Normal.

5. Aug 9, 2016

Orodruin

Staff Emeritus
In a collision without friction at the contact surface, there can be no force along the surface by definition.

Real impacts have friction, but note that a force in the travel direction would make the ball bounce back in the direction it came from. This is not the typical observation, but you can often make a ball bounce back by giving it a back spin.

6. Aug 9, 2016

UMath1

Can't a force be applied on the wall's surface at an angle though?

7. Aug 9, 2016

8. Aug 9, 2016

Orodruin

Staff Emeritus
Only if there is friction. It is the same as any other surface-surface interaction.

9. Aug 9, 2016

UMath1

Ok. Why is friction a minimal force in a non-ideal situation though? Ball bounces follow an almost perfect reflection trajectory.

10. Aug 10, 2016

A.T.

11. Aug 10, 2016

sophiecentaur

In the context of Snooker / Billiards, the friction is a very relevant factor and that situation is one of the nearest to ideal. If it were not, there would be no point (it would be impossible to do) in giving a ball spin.