Conservation of Mechanical Energy

  • Thread starter domtar
  • Start date
  • #1
6
0

Homework Statement



A 1.0 kg projectile is fired from a point on the earths surface at an angle θ = 45° with the horizontal and with an initial velocity v = 30 m/s. Neglect any effects due to air resistance and find:

a) What is the kinetic energy of the projectile when it reaches the highest point on its trajectory?
b) How much work was done in firing the projectile?

Homework Equations



total mechanical energy = KE + PE

KE_i + PE_i + W = KE_f + PE_f

The Attempt at a Solution



I'm not sure how to start this problem, or how to tackle it. I'm assuming I have to use the second equation? I let KE = 1/2 mv^2, m=1.0kg, v=30m/s. Then PE=mgh, m=1.0kg, g=9.81m/s/s, h=?. Then W=Fdcosθ, F=?, d=? cosθ=cos45°. Then I'm sort of stuck... There's a lot of values missing and I'm not sure how to solve or where to start.

Any help would be appreciated, thank you.
 

Answers and Replies

  • #2
ehild
Homework Helper
15,543
1,909
Hi domtar,

The keyword is "projectile". What do you know about projectile motion?

ehild
 

Related Threads on Conservation of Mechanical Energy

  • Last Post
Replies
8
Views
713
  • Last Post
Replies
1
Views
558
  • Last Post
Replies
2
Views
886
  • Last Post
Replies
6
Views
3K
  • Last Post
Replies
7
Views
2K
  • Last Post
Replies
11
Views
162
  • Last Post
Replies
2
Views
118
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
5
Views
2K
Top