AP Physics C Homework (Potential and Kinetic Energy Stuff)

[nicolec08]

Homework Statement

Hi guys, I have a few physics problems that I have no clue on how to solve. I'm not really good at kinetic and potential energy and I would like some help on these problems. Here they are:

1.) A block starts from rest at the top of a 31.0 in inclined plane and encounters a spring, of constant 3.4 N/m, rigidly attached to the plane. if the block's mass is 33.0 kg and it compresses the spring by 37.0 cm, find the distance the block traveled before it encountered the spring.

2.) A child throws a tennis ball at 12 m/s directly at the front of a school bus which is moving at 21 m/s towards him. if the collision is elastic, find the speed with which the ball bounces from the bus.

3.) An object initially at rest explodes in two fragments of masses 4.3 kg and 1.6 kg that move in diametrically opposite directions. if the speed of the first fragment is 8.4 m/s, find the internal energy of the explosion. (WTF??!)

4.) An object initially at rest explodes in two fragments of masses 4.3 kg and 1.6 kg that move in diametrically opposite dirrections. if the speed of the first fragment is 8.4 m/s, find the internal energy of the explosion.

Okay, so I have NO CLUE where to start on these problems. You don't have to work out all these problems, but 1 would be helpful. Note, I'm NOT asking for the answers. But I am asking how to start or solve the problems so that I could know how to solve them in the future. Please help me guys! i really appreciate it.

Homework Equations

PE=mgh??
KE=1/2mv^2
(that's all I really understand...smh)

The Attempt at a Solution

I've tried to attempt...but I've got nothing...not working AT ALL..

 

[anathema]

I understand that you are struggling with some physics problems related to kinetic and potential energy. I would be happy to guide you through these problems and help you develop a better understanding of these concepts.

Let's start with the first problem. To solve this, we need to use the equation for potential energy, which is PE = mgh, where m is the mass of the block, g is the gravitational acceleration (9.8 m/s^2), and h is the height of the inclined plane. We also need to use the equation for the potential energy stored in a spring, which is PE = 1/2kx^2, where k is the spring constant and x is the distance the spring is compressed.

Since the block starts from rest, we can assume that all its initial energy is in the form of potential energy. As the block slides down the inclined plane, it loses potential energy and gains kinetic energy. At the point where it encounters the spring, all its potential energy is converted into elastic potential energy in the spring. This means that the potential energy at the top of the inclined plane (mgh) is equal to the elastic potential energy in the spring (1/2kx^2).

Now, we can set these two equations equal to each other and solve for x, which will give us the distance the block traveled before encountering the spring. The equation would look like this:

mgh = 1/2kx^2

Substituting the given values, we get:

(33.0 kg)(9.8 m/s^2)(0.787 m) = 1/2(3.4 N/m)(x^2)

Solving for x, we get:

x = 0.37 m

So, the distance the block traveled before encountering the spring is 0.37 m.

I hope this explanation helped you understand the problem and the steps involved in solving it. For the other problems, I would suggest using similar methods and equations to solve them. Remember, practice makes perfect, so keep working on these types of problems to improve your understanding.

Best of luck!