Differences in velocity conceptual question

In summary, the conversation discusses the difference in velocities between two objects A and B and the equation for calculating restitution in one and two/three dimensions. The equation for coefficient of restitution is: e = (vB - vA) / (uA - uB), with a reversal in the order of A and B between numerator and denominator.
  • #1
Pochen Liu
52
2

Homework Statement


If I want to find the difference in velocities of 2 objects A and B
We know the sum of their velocities is A + B
But but is the difference B - A
Why not A - B?

Homework Equations


This is from the equation of calculating restitution where
(greek letter) = (The difference in the velocities after the collision)/(Difference in the velocities before the collision)

The Attempt at a Solution


N/A other than google which didnt help.
 
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  • #2
Your equation for the coefficient of restitution (if that is what you mean bt restitution) is not quite right. For collisions in one dimension, It is:
e = (vB - vA) / (uA - uB), where the v's denote velocities after collision and the u's denote velocities before collision. Note the reversal in order of A and B between numerator and denominator.
In two and three dimensions, you define the coefficient of restitution in terms of the components of the velocities along the line of impact.
 
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Likes Pochen Liu
  • #3
Ok, see I literally copy and pasted the schools scholarship 'formulae' in here. Good to know the equation actually specifies it in constants.
 

1. What is velocity?

Velocity is a measure of the rate of change of an object's position over time. It takes into account both the object's speed and direction of motion.

2. How is velocity different from speed?

Velocity and speed are closely related, but they are not the same. Speed is a scalar quantity that only considers the magnitude of an object's motion, while velocity is a vector quantity that also takes into account the direction of motion.

3. What factors affect an object's velocity?

An object's velocity can be affected by its mass, the forces acting on it, and its initial position and velocity. These factors can change the object's speed, direction, or both.

4. Can velocity be negative?

Yes, velocity can be negative. This indicates that an object is moving in the opposite direction of its initial velocity. For example, if a car is traveling east at 50 km/h and then turns around and travels west at 50 km/h, its velocity would be -50 km/h.

5. How is velocity calculated?

Velocity is calculated by dividing the change in an object's position by the change in time. It is often represented by the equation v = (xf-xi)/t, where v is velocity, xf is the final position, xi is the initial position, and t is the time interval.

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