Register to reply

Motion Problem

by eliassiguenza
Tags: motion
Share this thread:
eliassiguenza
#1
Mar22-11, 12:00 AM
P: 24
1. The problem statement, all variables and given/known data
A stunt man drives a car at a speed 20m/s off a 30m high cliff. The road leading to the cliff is inclined upward at an angle of 20 degrees.

How far from the base of the cliff does the car land?

What is the car's impact speed?

3. The attempt at a solution
I thought of just doing some old fashion R = V initial ^2 sin 2 alpha/g

since V = dx/dt

dt = dx/V

=30/ Sin alpha

now that I know dt y multiply by v cos alpha to then add it to R.
Apparently I'm wrong, could someone help me?
Phys.Org News Partner Science news on Phys.org
World's largest solar boat on Greek prehistoric mission
Google searches hold key to future market crashes
Mineral magic? Common mineral capable of making and breaking bonds
jhae2.718
#2
Mar22-11, 12:07 AM
PF Gold
jhae2.718's Avatar
P: 1,153
Quote Quote by eliassiguenza View Post
3. The attempt at a solution
I thought of just doing some old fashion R = V initial ^2 sin 2 alpha/g
You are correct; you can use [tex]r=\frac{v_0^2\sin(2\theta)}{g}[/tex].

To find the impact velocity, what kinematic equation relates range and time?

Then, what equation gives velocity in y as a function of time?
eliassiguenza
#3
Mar22-11, 12:19 AM
P: 24
[/QUOTE]
now that I know dt y multiply by v cos alpha to then add it to R.[/QUOTE]

Sorry I was meant to type and I multiply now, at impact shouldn't be
Vfinal = V initial + 1/2 gt ^2
???


Thanx For Helping! =)

jhae2.718
#4
Mar22-11, 12:33 AM
PF Gold
jhae2.718's Avatar
P: 1,153
Motion Problem

Quote Quote by eliassiguenza View Post
now that I know dt y multiply by v cos alpha to then add it to R.

Sorry I was meant to type and I multiply now, at impact shouldn't be
Vfinal = V initial + 1/2 gt ^2
???


Thanx For Helping! =)
[tex]\frac{1}{2}gt^2[/tex] will give you distance. The equation for velocity as a function of time is [tex]v(t)=v_0+gt[/tex], where the sign of g depends on what direction you call positive.


Register to reply

Related Discussions
Swing problem harmonic motion problem Advanced Physics Homework 1
Graphing Motion problem (motion in a straight line) Introductory Physics Homework 2
Projectile Motion + Linear Motion = Problem Introductory Physics Homework 3
Projectile Motion Problem! This problem is completely evading me. Introductory Physics Homework 4
Uniform Circualr Motion with Projectile Motion problem (Extremely confusing): Introductory Physics Homework 4