# Velocity Calculation - ball bouncing off a wall at an angle

• Molly1235
In summary, the conversation discusses the calculation of velocity for a ball bouncing off a wall at an angle. The question asks for the change in velocity of the ball at the bounce, given that it was initially launched at 45 degrees towards the wall at 4 m/s and bounced away at 45 degrees at 3 m/s. The person initially thought the answer was 7 m/s at an angle of 90 degrees, but the book states it is 5 m/s. After drawing a diagram and realizing their mistake, they confirm that the correct answer is indeed 5 m/s. They also mention being new to the world of vectors and thanking for the help.

#### Molly1235

Velocity Calculation -- ball bouncing off a wall at an angle

Question:

"A ball is locked at 45 degrees towards a wall at 4 m/s. It bounces away from the wall at an angle of 45 degrees at 3 m/s. Find the change in velocity of the ball at the bounce."

My attempt:

So I know that change in velocity = v-u.

Therefore I thought that the answer would be 3 - -4 (3+4) = 7 m/s at an angle of 90 degrees, however my book says the answer is 5 m/s.

I'm a little confused and would be grateful for some clarification. I'm thinking it must have something to do with it being the velocity at the bounce but I'm not sure?

Thanks in advance!
Molly

Draw the diagram.

EDIT:

I'm telling you to draw the diagram, because it'll probably help you. Try doing it with vectors.

Last edited:

What programs do you guys use to draw vectors and diagrams and etc? Seriously

I think I just manged to work it out - taken a picture but then realized I can't upload it from my mobile. I was being daft and drawing it wrong as I forgot an angle of 90 degrees forms against the wall (as in your diagram). Thank you! :)

1 person
Molly1235 said:
I think I just manged to work it out - taken a picture but then realized I can't upload it from my mobile. I was being daft and drawing it wrong as I forgot an angle of 90 degrees forms against the wall (as in your diagram). Thank you! :)

You're welcome. Let me know if you need any help.

Crake said:
You're welcome. Let me know if you need any help.

Thanks - I appreciate it. I'm completely new to the world of vectors so get a little confused sometimes :')

## 1. How is velocity calculated when a ball bounces off a wall at an angle?

The velocity of a ball bouncing off a wall at an angle can be calculated using the law of reflection, which states that the angle of incidence (incoming angle) is equal to the angle of reflection (outgoing angle). This means that the velocity of the ball after bouncing off the wall will have the same magnitude as its velocity before bouncing, but will be directed at a different angle.

## 2. What factors affect the velocity of a ball bouncing off a wall at an angle?

The velocity of a ball bouncing off a wall at an angle can be affected by factors such as the initial velocity of the ball, the angle at which it hits the wall, the elasticity of the ball and the wall, and any external forces acting on the ball.

## 3. How do you calculate the angle at which a ball will bounce off a wall?

The angle at which a ball will bounce off a wall can be calculated using the law of reflection. The angle of incidence (incoming angle) is equal to the angle of reflection (outgoing angle), so you can measure the incoming angle and use it to determine the outgoing angle.

## 4. Can the velocity of a ball bouncing off a wall at an angle ever be greater than its initial velocity?

No, the velocity of a ball bouncing off a wall at an angle cannot be greater than its initial velocity. This is because some of the energy of the ball is lost during the collision with the wall, due to factors such as friction and heat.

## 5. How does the mass of the ball affect its velocity when bouncing off a wall at an angle?

The mass of the ball does not directly affect its velocity when bouncing off a wall at an angle. However, the mass of the ball can affect the amount of force exerted on the wall and the amount of energy lost during the collision, which can ultimately affect the velocity of the ball after bouncing off the wall.