Physics help... looking for explanation, not just an answer?

Question

This is a HS physics class, so its not going to be very hard.


A 0.18 kg ball is places on a compressed spring on the floor. The spring exerts an average force of 2.8 N through a distance of 15 cm as it shoots the ball upward. How high will the ball travel above the release spring?

Thanks!

Answer 1

this is a conservation of energy problem...

the answer is to say that the energy imparted to the object is equal to the work done on it. this is given by W=Fd this, in turn, is equal to the total potential energy at the height of its trajectory given by mgh so setting both equations equal and solving for h gets you...

Fd = mgh

h = Fd/mg = (2.8*.15)/(.18*9.8) = 0.238 m with proper units

the idea here is conservation of energy. the work done on the ball is all converted to the potential energy as it climbs higher and higher.

Answer 2

Energy equation
Energy in the spring =
Es=Fx

The kinetic energy Ke of the ball when released =Es
Ke=Es

Ke = Pe
Pe is the potential energy the ball will obtain at the very top so
Pe = mgh

then
h=Es/(mg)
h=Fx/(mg)
h=2.8 x .15 / (.18 x 9.81)
h=23.8cm

You're welcome