Elastic potential energy of two blocks of mass

• TrippingBilly
In summary: Note that kinetic energy is not a vector quantity, it is scalar. You should therefore add the individual kinetic energies to obtain the potential.
TrippingBilly
Two blocks of masses M and 3M are placed on a horizontal, frictionless surface. A light spring is attached to one of them, and the blocks are pushed together with the spring between them. A cord initially holding the blocks together is burned; after this, the block of mass 3M moves to the right with a speed of 1.50 m/s.
(a) What is the speed of the block of mass M?
(b) Find the original elastic potential energy in the spring if M = 0.350 kg.

What factors determine the potential energy stored in a spring and how do they relate to each other?

It depends on how much is compresses or stretches, but that isn't known and as far as I know can't be calculated. It also depends on the stiffness of the spring but that isn't given either.

TrippingBilly said:
It depends on how much is compresses or stretches, but that isn't known and as far as I know can't be calculated.
Okay, sorry a little misleading perhaps. What quantities must be conserved here?

Momentum is conserved, and kinetic energy is conserved, so that means that potential energy must be conserved too. and change in kinetic energy = - change in potential energy..

Last edited:
TrippingBilly said:
Momentum is conserved, and kinetic energy is conserved, so that means that potential energy must be conserved too.
Energy is conserved, it can however, be transformed from one form to another (i.e. from potential to kinetic).

I think my problem was only calculating the kinetic energy of the smaller mass, because I thought if i calculated it for the system they would offset each other but they dont. So, KE=(.5)(.35)(.45^2) - (.5)(.35)(3)(1.5^2) = 2.3625 so potential energy is the opposite of that?

TrippingBilly said:
I think my problem was only calculating the kinetic energy of the smaller mass, because I thought if i calculated it for the system they would offset each other but they dont. So, KE=(.5)(.35)(.45^2) - (.5)(.35)(3)(1.5^2) = 2.3625 so potential energy is the opposite of that?
Note that kinetic energy is not a vector quantity, it is scalar. You should therefore add the individual kinetic energies to obtain the potential.

What is elastic potential energy?

Elastic potential energy is the energy stored in an object when it is stretched or compressed. It is a type of potential energy that is dependent on the displacement or change in shape of an object.

How is elastic potential energy related to two blocks of mass?

Elastic potential energy can be observed when two blocks of mass are connected by a spring or elastic material. The displacement of the blocks from their equilibrium position creates a potential energy that can be released as kinetic energy when the blocks are released.

What factors affect the amount of elastic potential energy in two blocks of mass?

The amount of elastic potential energy in two blocks of mass is affected by the stiffness of the material connecting the blocks, the distance the blocks are stretched or compressed, and the mass of the blocks themselves. A stiffer material and a greater displacement will result in a higher amount of elastic potential energy.

How is the elastic potential energy of two blocks of mass calculated?

The elastic potential energy of two blocks of mass can be calculated using the formula PE = 1/2kx^2, where PE is the elastic potential energy, k is the spring constant of the material, and x is the displacement of the blocks from their equilibrium position.

What are some real-life applications of elastic potential energy in two blocks of mass?

Elastic potential energy is used in many real-life applications, such as in trampolines, bungee jumping, and catapults. It is also important in understanding the behavior of materials and structures under stress, such as in engineering and construction.

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