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Acceleration problem 15

  • Thread starter Iceclover
  • Start date
59
0
Problem:
a rock is thrown vertically with a velocity of 20m/s from the edge of a bridge 42m above the river. how long does the rock stay in the air.

Equation:
d=vt+1/2at^2

Atempt at solution:
I've actually had a couple of attempts and i came up with a bunch of crazy things. I just need a hint, or to know if im using the correct formula.
 

Answers and Replies

cristo
Staff Emeritus
Science Advisor
8,056
72
Iceclover, please post in the homework forums in future.

Your equation for this question is correct. Please show your work, and we will be able to help.
 
103
0
A few good helpful hints is to do this first; label what you have and what you don't have and what you're trying to find. Then look at the equations you have; use algebra to isolate a variable and these types of problems will come a lot more easily.

Using Y's since this is acting in the Y direction, not the X direction. Also, since it's acting in the Y direction there's a force at work here =). Think about it.

Y (final position):
Yo (initial position):
Vy (final velocity):
Vyo (initial velocity):
a (acceleration):
t (time):

Hint: Your starting position will usually be 0 m. Unless told otherwise through the problem. Also, you can use a string of equations to solve for things =). Such as isolate the t, and then use that t for another equation =).
 
Last edited:

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