Finding the Post-Collision Velocity: Is My Calculation Correct?

In summary, when Daisy (65.0kg) skates at 4.5m/s and collides with her friend (75.0kg) who is standing still, they both move off together at a speed of 2.1 m/s. This is calculated using the equation (MaVa+MbVb) / (Ma+Mb).
  • #1
Mowgli
31
0

Homework Statement



Daisy (65.0kg) skates on ice at 4.5m/s to greet her friend (75.0kg), who is standing still, with open arms. As they collide, while holding each other, with what speed do the both move off together?


Homework Equations



MaVa+MbVb / Ma+Mb


The Attempt at a Solution



Is this correct?

(Va+b)=75(0)+(65)(4.5) / 75+65
= 0+69.5 / 140
= .496m/s
 
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  • #2
using the equation

m1v1 + m2v2 = (m1 + m2)vf

I think you forgot to multiply the speed of Daisy to her mass.
 
  • #3
Mowgli said:

The Attempt at a Solution



Is this correct?

(Va+b)=75(0)+(65)(4.5) / 75+65
= 0+69.5 / 140
= .496m/s
(65)(4.5)=/=69.5
Multiplication not addition.
 
  • #4
Mowgli said:

Homework Equations



MaVa+MbVb / Ma+Mb
Careful with parentheses. This should be: (MaVa+MbVb) / (Ma+Mb)

Redo your calculation.
 
  • #5
So I got (75(0) + 65(4.5)) / (75+65)
= 0+292.5 / 140
= 2.1 m/s
 
  • #6
that's correct :biggrin:
 
  • #7
thank you so much!
 

1. What is a collision?

A collision occurs when two objects come into contact with each other and exert a force on each other. This can result in a change in the motion or shape of the objects involved.

2. What is impulse?

Impulse is the product of force and time, and is equal to the change in momentum of an object. It is often used to describe the impact or force of a collision.

3. How is momentum related to collisions?

Momentum is a measure of an object's mass and velocity. In a collision, the total momentum of the objects before and after the collision must be conserved, meaning it remains the same. This is known as the law of conservation of momentum.

4. What factors affect the force of a collision?

The force of a collision is affected by the mass and velocity of the objects involved. The greater the mass and velocity, the greater the force of the collision will be.

5. How do elastic and inelastic collisions differ?

Elastic collisions involve objects that bounce off each other and conserve both momentum and kinetic energy. Inelastic collisions involve objects that stick together or deform, and do not conserve kinetic energy. Some kinetic energy is usually lost in an inelastic collision due to friction or other factors.

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