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

Projectile motion off a ramp

  • Thread starter DRC12
  • Start date
  • #1
41
0

Homework Statement


A skateboarder starts up a 1.0--high, 30 ramp at a speed of 7.9 . The skateboard wheels roll without friction. How far from the end of the ramp does the skateboarder touch down?


Homework Equations



x=x0+v0t+.5(a)(t2)
v=v0+at

The Attempt at a Solution


This question seems pretty straight forward and I've found an answer but the website we use says it's wrong. First I found vx=7.9cos(30)=6.84 and vy=7.9sin(30)=3.95. I tried finding maximum y by solving vy=0=-9.8*t1 then t1=.405 and plugging that into y=1.8 then finding t2 when y=0 and y0=1.8 to get t2=.605 so ttotal=1.01 and plugging that into x=6.913
 

Answers and Replies

  • #2
1,065
10
A skateboarder starts up a 1.0--high, 30 ramp at a speed of 7.9 . The skateboard wheels roll without friction. How far from the end of the ramp does the skateboarder touch down?
-------------------
My understanding that it starts off a flat ramp top.
I do not understand whether the friction has any factor in the calculation.
With zero initial vertical velocity, in my calculation the distance from the base is 1.8m
 
  • #3
41
0
sorry 30 ramp is supposed to be 30o ramp
 
  • #4
Simon Bridge
Science Advisor
Homework Helper
17,847
1,644
What immediately occurs to me is that the ground (where the skateboarder touches down) is at a different height to the end of the ramp (where ballistic motion starts).
The 7.9m/s is at the bottom of the ramp, not the top.
 
  • #5
41
0
Yeah that was it the 7.9 was at the bottom of the ramp not the end of the ramp thanks
 

Related Threads on Projectile motion off a ramp

  • Last Post
Replies
5
Views
10K
  • Last Post
Replies
7
Views
13K
  • Last Post
Replies
8
Views
10K
  • Last Post
Replies
5
Views
3K
Replies
21
Views
11K
  • Last Post
Replies
1
Views
1K
Replies
3
Views
2K
  • Last Post
Replies
10
Views
3K
Replies
5
Views
20K
Replies
1
Views
5K
Top