How do I find the final velocity and how high the bridge is?

  • #1
Julia Smith

Homework Statement


A rock that is thrown upward from a bridge with an initial velocity of 2.0 m/s. (Assume there is no air drag: a = -10m/s2).
a) If the rock takes 4.0 s to hit the water below once the rock is released. What is the final velocity of the rock as it hits the water?
b) How high is the bridge?

Homework Equations


v = u +at
x = x0 + vit + 1/2*a*t2

The Attempt at a Solution


For (a), I know that the equation I can use is v = u + at. u being initial velocity.
v = (2.0m/s) + (-10m/s2) (4.0s)
v = -38 m/s

However, for (b), I do not know how I can solve it and need help on that ASAP
 

Answers and Replies

  • #3
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,073
Hi Julia Smith. :welcome:

Your equation is right if x is displacement, so just treat xo as zero.

I'd prefer the equation be written using s for displacement, viz.,
s = ut + ½at2

where s is the displacement due to this acceleration.
You can throw in a term so if you wish, but it seems an unnecessary complication.
 

Related Threads on How do I find the final velocity and how high the bridge is?

Replies
10
Views
732
  • Last Post
Replies
2
Views
660
Replies
1
Views
1K
Replies
17
Views
541
  • Last Post
Replies
12
Views
7K
  • Last Post
Replies
3
Views
1K
Replies
15
Views
2K
Top