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

Simple Kinematics problem

  • Thread starter vivienwest
  • Start date
  • #1

Homework Statement



A small steel ball, dropped from rest, takes 0.5s to fall through a vertical distance of 1.25m.
Determine the actual speed of the ball when it has fallen through a vertical distance of 1.25m, assuming that acceleration is constant.


Homework Equations



v=s/t

The Attempt at a Solution



Long ago I was helped by a friend to get the result
( 1.25m x 2 ) / 0.5s = 5ms-1

but I've forgotten how did he come to that conclusion, and the reason behind (1.25mx2), help is much appreciated .
 

Answers and Replies

  • #2
Cyosis
Homework Helper
1,495
0
The formula [itex]s=vt[/itex] is only valid for constant speed. Does an object fall with constant speed?

Your friend used the following, correct equations:

1) [itex]s=\frac{1}{2}at^2+v_0t+x_0[/itex]
2) [itex]v=at+v_0[/itex]

These are valid for constant acceleration. You will need to combine both of them to get the answer.
 
  • #3
181
0
s = t*(u+v)/2
 

Related Threads for: Simple Kinematics problem

  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
2
Views
564
  • Last Post
Replies
14
Views
2K
  • Last Post
Replies
6
Views
1K
  • Last Post
Replies
8
Views
4K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
3
Views
898
Top