• Support PF! Buy your school textbooks, materials and every day products Here!

Two Dimensional Motion (I)

  • Thread starter Aggie
  • Start date
  • #1
21
0
I am stumped big time!

Two runners start at the same point on a straight track. The first runs with a constant acceleration so that he runs 93 yards in 8 seconds. The second runner waits 3 seconds and then throws a rock at his opponent's head. If the head and the rock are at the same level form the grownd, what must the inital magnitude of the velocity be if the rock is to hit the head just at the 93 yard tape?
 

Answers and Replies

  • #2
andrevdh
Homework Helper
2,128
116
What distance does the rock need to cover in how much time?
 
  • #3
21
0
The same distance as the runner who actually runs covers but the time is unknown
 
  • #4
cristo
Staff Emeritus
Science Advisor
8,107
73
Is it? The stone must hit the runner as he reaches the finish line. You know the time that this happens, so can you say what the time that the stones takes in the air is?
 
  • #5
21
0
the stone takes 5 secs in the air
 
  • #6
cristo
Staff Emeritus
Science Advisor
8,107
73
Yup, so now can you set up a relevant equation?
 
  • #7
21
0
how do you get the vertical component of velcocity.

you get the horizontal component of velocity with what you have - 93/5 = 18.6 yrds/sec
 
  • #8
cristo
Staff Emeritus
Science Advisor
8,107
73
For the horizontal component, you have used the equation d=ut+at2/2, where u is the initial velocity. Set up a similar equation in the y direction; you know d, a and t, so you can solve for uy.
 
  • #9
21
0
the vertical height is not given. unless we use zero
then we get 24.5
 
  • #10
21
0
Please can you explain this because it makes no sense. We don't know the vertical distance
 

Related Threads on Two Dimensional Motion (I)

  • Last Post
Replies
1
Views
864
  • Last Post
Replies
4
Views
3K
  • Last Post
Replies
4
Views
982
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
6
Views
11K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
8
Views
629
  • Last Post
Replies
10
Views
1K
Top