# Velocity Change When Hitting a Wall

• DeanBH
In summary, when an object moving at a given velocity hits a wall and is in contact with it for a certain amount of time (0.2 seconds in this case), the change in velocity (or acceleration) will be in the opposite direction (-) of the initial velocity. This is assuming no resistance from air or other factors. The time becomes important when calculating impulse or acceleration.
DeanBH
if something is moving at a wall with a given velocity. and is in contact with the wall for say 0.2 seconds.

the chance in velocity for those 0.2 seconds would be (-) the velocity it hit it win?

the chance in velocity for those 0.2 seconds would be (-) the velocity it hit it win?

?

Could you perhaps try again?

hypothetical

ignore resistances of air and things

if something is moving at a wall with a given velocity. and is in contact with the wall for say 0.2 seconds.

the change in velocity for those the time it is in contact will the wall, would be (-) the velocity it hit it with?

there's no point in being so picky when you know exactly what i mean

Last edited:
Hey … DeanBH … I didn't understand it either!

Still not sure I do … the 0.2 seconds seems irrelevant …

If the ball just squished against the walll and stopped dead, then the change in velocity would be (-) the velocity it hit it with.

If the collision was perfectly elastic, the change in velocity would be twice that.

In reality, almost nothing (aside from maybe a sandbag or a lead-filled snowshoe) will just stop dead with no rebound. Also, even those things would gain an immediate downward velocity due to gravity unless the wall is out in space somewhere.

The ball is thrown into the wall a specific angle, leaving the thrower's hands with a specific amount of force, traveling in an arc-like path to hit a wall, thus causing some of the energy to dissipate as sound and heat, and bouncing off the wall at a downward angle.

You gave a single number: 0.2 s. which defines how long the ball was in contact with the wall.

That number has absolutely no significance, whatsoever. All you've done here is give the image of a ball hitting a wall, here.

DeanBH said:
if something is moving at a wall with a given velocity. and is in contact with the wall for say 0.2 seconds.

the chance in velocity for those 0.2 seconds would be (-) the velocity it hit it win?

The change in velocity is called the acceleration. Say your object moves from left to right, then contracts the wall. The change in velocity, or acceleration is (-), as you say is in the other direction, from right to left. I think this is what you've been asking about.

Just think about it this way. $$\Delta V=V_{final}-V_{initial}$$ so, if the initial velocity is 5 m/s and it comes to a dead stop, $$\Delta V=-5m/s$$. Assuming no mass loss, $$\Delta \vec{P}=m\Delta \vec{V}=\vec{F}\cdot t$$

When doing impulse or the acceleration, that is when the time matters.

## 1. How does the velocity of an object change when it hits a wall?

When an object hits a wall, its velocity changes due to the impact force from the collision. The magnitude and direction of the velocity change depend on the mass and speed of the object, as well as the stiffness and angle of the wall.

## 2. Does the velocity of the object always decrease when it hits a wall?

No, the velocity of the object does not always decrease when it hits a wall. If the wall is angled or the object bounces off the wall, the velocity can actually increase. However, in most cases, the velocity will decrease due to the energy lost during the collision.

## 3. What is the relationship between the velocity change and the mass of the object?

The velocity change is directly proportional to the mass of the object. This means that a heavier object will experience a larger change in velocity compared to a lighter object when hitting a wall with the same force.

## 4. How does the stiffness of the wall affect the velocity change?

The stiffness of the wall plays a major role in determining the velocity change of an object after impact. A stiffer wall will result in a larger velocity change due to the higher force exerted on the object during the collision.

## 5. Can the direction of the velocity change be predicted?

Yes, the direction of the velocity change can be predicted using the law of conservation of momentum. The velocity change will always occur in the direction opposite to the initial velocity of the object, known as the rebound direction.

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