Projectile: Find initial velocity without time


by JJBladester
Tags: angle, projectile, time, velocity
JJBladester
JJBladester is offline
#1
Sep11-10, 11:25 AM
PF Gold
JJBladester's Avatar
P: 280
1. The problem statement, all variables and given/known data
Knowing that snow is discharged at an angle of 40 degrees, determine the initial speed, v0 of the snow at A. Answer: 6.98 m/s


2. Relevant equations





3. The attempt at a solution

I have found the x and y velocity and position formulas. Now since I don't know time, should I solve both position equations for time (t) and set them equal to each other to get my only unknown, vi? The quadratic equation for time in the y-dir seems a bit hectic. Is there an easier way to go about trying to find vi?
Phys.Org News Partner Science news on Phys.org
Review: With Galaxy S5, Samsung proves less can be more
Making graphene in your kitchen
Study casts doubt on climate benefit of biofuels from corn residue
kuruman
kuruman is offline
#2
Sep11-10, 09:25 PM
HW Helper
PF Gold
kuruman's Avatar
P: 3,444
Start with
L = v0 t cosθ
Δy = v0 t sinθ - (1/2) g t2

Solve the first equation for t and replace in second equation. Solve the ensuing equation for v0.
JJBladester
JJBladester is offline
#3
Sep12-10, 07:47 AM
PF Gold
JJBladester's Avatar
P: 280
Quote Quote by kuruman View Post
Start with
L = v0 t cosθ
Δy = v0 t sinθ - (1/2) g t2

Solve the first equation for t and replace in second equation. Solve the ensuing equation for v0.
I believe this is what you had in mind. The answer matches the professor's answer. Thanks again kuruman!



Register to reply

Related Discussions
Projectile motion without time and initial velocity Introductory Physics Homework 16
Finding the initial velocity of a projectile, given time, an angle, and distance Introductory Physics Homework 2
How to find initial velocity in projectile motion problem..? Introductory Physics Homework 12
Find initial velocity of a projectile (v0) given displacement, time and acceleration? Introductory Physics Homework 6
Projectile motion (No initial velocity or time) Introductory Physics Homework 3