Science Forums

# Need Help With This Physical Science Hw! (Hard)

## Recommended Posts

thanks for any help!

##### Share on other sites

thanks for any help!

These 3 problems are pretty easy, wigz!

Rather than one of our members just answer them, I recommend you post your answers, and we check them and help you by showing any mistakes or misunderstandings.

We all learn best by trying 'til we get things right.

##### Share on other sites

These 3 problems are pretty easy, wigz!

Rather than one of our members just answer them, I recommend you post your answers, and we check them and help you by showing any mistakes or misunderstandings.

We all learn best by trying 'til we get things right.

im not good at science im completely lost!

##### Share on other sites

Well, let’s start by simplifying Newton’s laws of motion about as much as we can, so they state: “nothing changes its velocity unless acted upon by a force”. Now apply that to you question #1, “a car and a trailer are interacting as they move down the highway ... a. What is the interaction with the car and the trailer … b. what is causing the car to move down the highway?” Can you describe some of the source of force on the bodies we’re calling “the car” and “the trailer”? And, can you name the term for the quality bodies have of not changing velocity unless acted upon by a force?

Question #2, you should be able to reason out intuitively, remembering that the acceleration of gravity can be considered constant for problems on this scale. If something accelerates at a constant rate from a speed of starting speed of V to 0 in a certain distance, then for the same distance and acceleration, starting at 0, to what speed will it accelerate? Answer this question, and see if you can apply it to question #2.

For question #3, you’re gonna need a couple of things. First, you need the equation for conservation of momentum. In words, it’s “multiply the mass of each body in a system (that’s not subject to any outside forces) times its velocity, add them all together, and the result doesn’t change. You should be able to write this for a system with 2 bodies in it something like

M1V1 before + M2V2 before = M1V1 after + M2V2 after

Now, see if you can figure out what the two bodies in this problem are, and their masses and velocities. The problem doesn’t just give you all the info – you’ve got to make an assumption to get one velocity.

Then you’ll need to write and do a little bit of simple algebra to get the answer, and show that you really understand how.

Hint: the velocity of the bodies V1 after and V2 after are equal in the “after” picture, and is the answer to the question.

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.