# Elastic potential energy

• jasonbans
In summary, the problem involves a horizontal spring with a force constant of 12N/m and a marble with a mass of 8.3 x 10^-3kg being shot at a target 93.0 cm below. The spring is initially compressed 4.0 cm and the marble is projected with an initial velocity of 1.52m/s using the law of conservation of energy. The remaining problem can be treated as projectile motion, where the vertical and horizontal motions are independent and can be solved using linear motion equations.

## Homework Statement

A horizontal spring, of force constant 12N/m, is mounted at the edge of a lab bench to shoot marbles at targets on the floor 93.0 cm below. A marble of mass 8.3 x 10^-3kg is shot from the spring, which is initially compressed a distance of 4.0 cm. how far does the marble travel horizontally before hitting the floor?

Ee= 1/2kx^2
Ep=mgh
Ek=1/2mv^2 ?
W= Fd?

## The Attempt at a Solution

not sure how to start it off

First let us find the initial velocity with which the marble is projected.

What principle do you think we will use?

Start by figuring how fast the marble is moving when it leaves the spring.

ok i did that and i got 1.52m/s by using the law of conservation energy "Ee=Ek"

correct

jasonbans said:
ok i did that and i got 1.52m/s by using the law of conservation energy "Ee=Ek"
Good.

Now you can treat the rest as a projectile motion problem. How long does it take for the marble to hit the floor?

Now this is the speed with which the marble is projected horizontally onto the floor below.

we never have touch upon projectile motion in class. is there some other method?

in projectile motion the vertical motion is independent of the horizontal motion.

Hence one can treat projectile motion as the resultant of two linear motions. So just work in linear motion. But be careful whether you are working in the vertical or in the horizontal.