Calculate the change in the total kinetic energy

In summary, on a frictionless, horizontal air table, a collision occurs between puck A (with mass 0.245 kg) and puck B (with mass 0.360 kg), where puck A has a velocity of 0.115 m/s to the left and puck B has a velocity of 0.660 m/s to the right after the collision. To calculate the change in total kinetic energy of the system, the initial velocity of puck A needs to be determined using conservation of momentum. Puck B's initial kinetic energy is zero, but this is only relevant if all initial momentum is in puck A. The initial velocity cannot be zero for the collision to occur.
  • #1
emeraldempres
30
0
On a frictionless, horizontal air table, puck A (with mass 0.245 kg) is moving toward puck B (with mass 0.360 kg), that is initially at rest. After the collision, puck A has a velocity of 0.115 m/s to the left, and puck B has velocity 0.660 m/s to the right.

Calculate the change in the total kinetic energy of the system that occurs during the collision.

I tried putting it all into the change of kinetic energy equation but it does not work, this is my equation

.5(.245 kg)(-.155^2)+ .5(.36)(.66^2)= .08 J

But that answer is wrong, can smeone help?
 
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  • #2
What's the initial velocity of puck A? Use that to find the initial KE of the system.
 
  • #3
The initial velocity i believe to be 0 m/s because the answer does not specify. using this, since the ke is equal to .5mv^2, the initial ke is 0 J. am i on the right track?
 
  • #4
Here, you have to solve for the initial conditions of the system. Puck A had some velocity that you can solve for using conservation of momentum, so its kinetic energy is not zero.

Puck B's initial kinetic energy is zero, though. But that's only important insofar that all of the initial momentum is in puck A.
 
  • #5
emeraldempres said:
The initial velocity i believe to be 0 m/s because the answer does not specify. using this, since the ke is equal to .5mv^2, the initial ke is 0 J. am i on the right track?
The initial speed cannot be zero, otherwise there would be no collision:
emeraldempres said:
On a frictionless, horizontal air table, puck A (with mass 0.245 kg) is moving toward puck B
Make sure you post the complete problem exactly as it was given.
 

1. What is kinetic energy?

Kinetic energy is the energy that an object possesses due to its motion. It is defined as the energy an object has as a result of its mass and velocity.

2. How do you calculate the change in total kinetic energy?

The change in total kinetic energy can be calculated by subtracting the initial kinetic energy from the final kinetic energy. The formula is: ΔKE = KEfinal - KEinitial.

3. What units are used to measure kinetic energy?

Kinetic energy is typically measured in joules (J) in the SI system of units. In some cases, it may also be measured in electron volts (eV) or foot-pounds (ft-lb).

4. What factors affect the amount of kinetic energy an object has?

The amount of kinetic energy an object has is affected by its mass and velocity. The greater the mass and/or velocity of an object, the greater its kinetic energy will be.

5. Can the total kinetic energy of a system ever be negative?

No, the total kinetic energy of a system cannot be negative. Kinetic energy is a scalar quantity and cannot have a negative value. However, the change in kinetic energy (ΔKE) can be negative if the final kinetic energy is less than the initial kinetic energy.

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