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Two Physics Questions - Please Help!

getjacked63

Member
Question #1


A ball of mass 0.5 kg is tossed upward into the air. When it leaves your hand, it has a kinetic energy of 138 Joules. Use conservation of energy to find how high it goes. (Ignore air resistance)





Question #2


A roller coaster car with a mass of 265.3 kg starts from a height of 114.9 meters above the ground just before rolling down the frictionless track. Using conservation of energy, find the speed of the car just as it reaches the ground.


After the car reaches the ground, it travels horizontally on the track, where a frictional force of 999.6 Newtons slows the car to a stop. What is the work done on the car in bringing it to rest?


How far will the car go before it comes to rest?



I don't have a clue what I am doing, I SUCK at physics! Thanks for the help!
 
Question 1:

potential energy = the mass of the object times the acceleration due to gravity times the height that the object is lifted

Ug = mgh

138 joules = .5(kg) * 9.8 (Gravity) * X (Height)

My guess is 28.163 Meters
 
helll yeah. thanks jimbo. your the man!! i also got #2 figured out now, so no need for anyone to waste their time on that.
 
Potential Energy (PE)= Weight*Height
=265.3 kg* 9.8 m/s/s *114.9 meters

Kinetic Energy (KE)= 1/2 * Mass * velocity^2
**At ground level, KE=PE
so Velocity = Square root of (2PE/mass)


Work is a form of energy. Work to stop a moving object is equal to the loss in the objects kinetic energy. Since the Kinetic energy in this case is equal to potential, PE=KE=Work

Therefore,
Distance traveled = PE/999.6 Newtons
 
African or European?
 
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