The hockey captain, a physics major, decides to measure the speed of the hockey puck, He loads a small styrofoam chest with sand, giving it a total mass of 6.4 kg. He places the chest and embeds itslef in the styrofoam. The chest moves off at 1.2 m/s. What was the puck's speed?
I know that the speed is 49m/s.
What was the kinetic energy of the puck before it hit the styrofoam? Not sure how to do this?
What was the kinetic enry of the chest with the puck in it after they moved away. Not sure how to do this?
How much mechanical energy was lost in this ellastic collision? Not sure how to do this either?
Any help on these would be greatly appreciated.
This looks like a conservation of momentum problem, but this sentence makes no sense:
"He places the chest and embeds itslef in the styrofoam."
I supposes what he is imbeds in the styrafoam and sand chest is the hockey puck, not himself.
It seems to me you need to know the mass of a hockey puck to do this problem. NHL hockey pucks can weigh between 156 and 170 gm. If we use 163 gm,
0.163 Vpuck = (6.4 + 0.2)*1.2 m/s
Vpuck = 49 m/s
That agrees with your "book" answer. The other questions are just number crunching
To answer these questions, we need to understand some principles of physics and equations related to kinetic energy and elastic collisions.
1. Kinetic Energy of the Puck before hitting the styrofoam:
The kinetic energy (KE) of an object can be calculated using the equation:
KE = 0.5 * mass * velocity^2
In this case, we know the mass of the puck is not given, but we can calculate it by subtracting the mass of the styrofoam chest from the total mass:
mass_puck = total mass - mass_styrofoam chest (which is 6.4 kg - mass_styrofoam chest)
Once we know the mass of the puck, we can calculate its initial kinetic energy.
2. Kinetic Energy of the Chest with the puck after moving away:
Assuming there is no external forces acting on the system (no friction, etc.), the total kinetic energy before and after the collision will be the same. So we can use the same equation to calculate the kinetic energy of the chest with the puck, given their total mass and final velocity.
3. Mechanical Energy Lost in the Elastic Collision:
Since we are dealing with an elastic collision, the kinetic energy lost in the collision will be converted into other forms of energy, such as elastic potential energy or sound.
To calculate the mechanical energy lost in the collision, you need to find the difference between the initial and final kinetic energies of the system.
Remember that when calculating kinetic energy, it's important to use consistent units (e.g., kilograms for mass, meters per second for velocity) to ensure the accuracy of the results.
I hope this explanation helps you understand how to approach and solve these problems.