The work done by the friction force to stop the player is equal to his loss of kinetic energy:

The work done by the friction force is the magnitude of the force

times the distance covered by the player, d:

The loss in kinetic energy is simply equal to the initial kinetic energy of the player, since the final kinetic energy is zero (the player comes to rest):

Substituting into the first equation, we get:

from which we find d, the distance covered by the player:
Stored energy=energy that is stored and may not be used, conservation of energy= saved energy that you can use for other things.
We know the equation of motion v = u+ at, where v is the final velocity, u is the initial velocity, a is the acceleration and t is the time taken.
In this case Final velocity before collision = 115 km/hr = 115*5/18 = 31.94 m/s
Time taken by car to reach this velocity = 8.83 seconds
Initial velocity = 0 m/s
v = u +at
31.94 = 0 + a*8.83
a = 3.62 
So acceleration of car just before collision = 3.62 
Answer: 2.61 s
Explanation:
We are given the following data:
is the initial height of the object
is the initial height of the object
In addition, the motion of the object is given by:
(1)
Where:
is the final height of the object
is the time the object is in the air before hitting the ground
Rewritting (1) with the given data:
(2)
Solving the quadratic equation with the quadratic formula
, where
,
,
and choosing the positive value of time:
(3)
(4) This is the time
-- Power used when the heater is running =
V²/R = (240)²/4.8= 12,000 watts. (<u>12 KW</u>)
(A gigantic heater ... suitable for maybe a theater, not for a home.)
-- Energy consumed in one day:
(12 KW) x (24 hours) x (25%) = <u>72 KwH per day</u>
-- Energy consumed in 30 days: (72 KwH/day) x (30 days) =
<u>2,160 KwH in 30 days</u>
-- Cost = ($0.1 / KwH) x (2,160 KwH) = <em>$216.00</em> in 30 days