Recoil velocity on frictionless surface

In summary, the recoil velocity of the child throwing a snowball on frictionless ice can be estimated by using the momentum equation, as in this scenario kinetic energy is not conserved. However, in cases where there are no external forces or energy losses, the kinetic energy equation can be used to estimate the final velocity.
  • #1
Valenti
15
0

Homework Statement


A child stands on frictionless ice and throws a snowball. Estimate the recoil velocity of the child.

Homework Equations


m1v1i + m2v2i =m1v1 +m2v2f
1/2mv21i + 1/2 mv22i = 1/2 mv21f + 1/2mv22f

The Attempt at a Solution


After choosing estimates for weight of snowball, speed of child throwing snowball and weight of child I plugged it into the momentum and kinetic energy laws and solved for the final velocity in both of them, but I am not sure which equation is supposed to be used and in what situations
 
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  • #2
Show your work in detail.
 
  • #3
gneill said:
Show your work in detail.
Thanks, checked my work again and noticed i forgot to sq root for Vf in the KE formula, since it was negative only the momentum equation works. What type of questions would the KE formula be used though?
 
  • #4
Kinetic energy is conserved when no external forces act on the system, or when there are no other avenues for energy loss or gain from the system. In perfectly elastic collisions kinetic energy is conserved. In inelastic collisions kinetic energy is not conserved.

A person throwing an object is equivalent to a "reverse" inelastic collision, where two bodies that were once connected are separated by some energy being injected: the person throwing the snowball is providing energy via their muscles, which is not accounted for by the simple conservation of KE formula applied to the individual masses.
 

1. What is recoil velocity on a frictionless surface?

Recoil velocity on a frictionless surface is the velocity at which an object will move in the opposite direction when a force is applied to it. This is due to the conservation of momentum, where the momentum of the object is equal and opposite to the momentum of the force applied.

2. How is recoil velocity calculated?

The recoil velocity can be calculated using the formula v = m/s, where v is the recoil velocity, m is the mass of the object, and s is the speed at which the force is applied. This formula assumes a perfect, frictionless surface.

3. What factors affect the recoil velocity on a frictionless surface?

The recoil velocity is affected by the mass of the object, the speed at which the force is applied, and the angle at which the force is applied. These factors can all be manipulated to change the resulting recoil velocity.

4. Can the recoil velocity be greater than the applied force?

No, the recoil velocity cannot be greater than the applied force. The momentum of the object will always be equal and opposite to the momentum of the force applied, so the recoil velocity will always be limited by the force applied.

5. How does friction affect the recoil velocity?

Friction will decrease the recoil velocity on a surface. This is because friction is a force that acts in the opposite direction of motion, so it will decrease the momentum of the object and therefore decrease the resulting recoil velocity.

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