To find the final velocity, you use the fact that the initial
momentum (mass x velocity) of both players must equal the final momentum
of the players:
(mass player 1 x velocity player 1) + (mass player 2 x
velocity player 2) = combined mass x final velocity
Notice that in the above equation we know all the variables
except for the final velocity. We solve for this and get:
final velocity = |
[(mass player 1 x velocity player 1) + (mass player 2
x velocity playe r2)] |
combined mass |
The energy comes out in a metric unit called a "joule".
A joule is not a lot of energy. It's about the amount of energy you'd use
to lift an apple to the height of your waist (1 meter).
To find the stoping force, we assumed the collision between
the players took about 1/4 of a second. Knowing this, we can look at the
change in momentum of either player and use the formula:
force = |
change-in-momentum |
time of impact |
According to Newton's third law -- for every action there
is an equal and opposite reaction -- each player must experience the same
force.
To calculate the time a lightbulb burns, all you need to
know is that when you use one joule per second, that's one watt. We divided
the final energy by 60 to calculate the time in seconds. |