# How Do You Calculate the Height of a Wedge in a Physics Problem?

• parwana
In summary, the block of mass m1 is released from rest at the top of a curved wedge of mass m2 = 2.00 kg, which sits on a frictionless horizontal surface. When the block leaves the wedge, its velocity is measured to be 4.00 m/s to the right.
parwana
A small block of mass m1 = 0.300 kg is released from rest at the top of a curved wedge of mass m2 = 2.00 kg, which sits on a frictionless horizontal surface as in Figure P6.59a. When the block leaves the wedge, its velocity is measured to be 4.00 m/s to the right, as in Figure P6.59b.

(a) What is the velocity of the wedge after the block reaches the horizontal surface?
I found the velocity to be -.6 m/s. I did 0=m2v2 + M(block)V(block)

(b) What is the height h of the wedge?

I know the energy equation will be

mgh= .5mv^2

If you find the velocity of the block and the wedge, you should be able to apply concervation of energy to determine the height of the wedge. This means one point you have to apply the formula to is when M1 is at rest at the top of the wedge. use mgh = (whatever you decide) to determine the height of M1 relative to the ground. This is the same as the height of the wedge.

I still don't understand. Can you show me how to set up the equation

Would it be

mgh= .5mv^2 Now which mass and which velocity should I use to find h here

parwana said:
I still don't understand. Can you show me how to set up the equation

Would it be

mgh= .5mv^2 Now which mass and which velocity should I use to find h here

As AVD said, you have to use conservation of energy on the system consisting of the block and the wedge. So, write down the sum of kinetic and potential energy for these two momens and set them to equal one another; a) the block rests on the wedge, b) the block is on the horizontal surface.

^ I am really sorry, I tried setting it up but I am getting it wrong.

would it be?

KE + PE = KE + PE

and go from there?

I tried that

.5(.3)(4^2) + .3(9.8)h= .5(32)(.6^2) + 2(9.8)h

is that right

It didnt work for some reason, I got .112 is height, or am I doing something wrong

am I showing in notes from that this may be an inelastic collision (m1v1i + m2v2i = (m1 + m2)Vf)... sorry I am not help to you :(

rkslperez04 said:
would it be?

KE + PE = KE + PE

and go from there?

PE(block) = KE(block) + KE(wedge), where PE(block) is for the moment the block is resting on the wedge, and KE(block) and KE(wedge) are for the moment when the block is on the horizontal surface, and the wedge has the velocity you calculated in part 1.

^ Its ok, I hope someone else helps

Thanks so much radou, but why don't we use the PE of the wedge?

parwana said:
Thanks so much radou, but why don't we use the PE of the wedge?

The wedge has no potential energy, since it is on the horizontal surface all the time.

^ oh ok thanks a lot

## 1. What is the difference between momentum and energy?

Momentum is a measure of an object's mass and velocity, while energy is a measure of an object's ability to do work or cause change. While both are related to an object's motion, they are fundamentally different concepts.

## 2. How is momentum calculated?

Momentum is calculated by multiplying an object's mass by its velocity. The formula for momentum is p = m * v, where p is momentum, m is mass, and v is velocity.

## 3. What is the law of conservation of momentum?

The law of conservation of momentum states that the total momentum of a closed system remains constant, meaning that the total momentum before an event is equal to the total momentum after the event. This law is based on the principle that momentum cannot be created or destroyed, only transferred between objects.

## 4. How does energy relate to momentum?

Energy and momentum are related through the concept of kinetic energy. Kinetic energy is the energy an object possesses due to its motion, and it is directly proportional to an object's mass and the square of its velocity. This means that as an object's momentum increases, its kinetic energy also increases.

## 5. Can an object have momentum without having energy?

Yes, an object can have momentum without having energy. This is possible because momentum is dependent on an object's mass and velocity, while energy is dependent on an object's mass, velocity, and position. Therefore, an object can have momentum due to its mass and velocity, even if it is not in motion or has no kinetic energy.

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