Projectile: Find initial velocity without time

Click For Summary
To find the initial velocity of snow discharged at a 40-degree angle without knowing time, the discussion suggests using the equations for horizontal and vertical motion. By solving the horizontal motion equation for time and substituting it into the vertical motion equation, the initial velocity can be determined. The proposed method leads to a solution that matches the professor's answer of 6.98 m/s. The approach emphasizes the importance of manipulating equations to eliminate unknowns. This technique effectively resolves the problem without directly calculating time.
JJBladester
Gold Member
Messages
281
Reaction score
2

Homework Statement


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

Homework Equations



snow%20thrower.jpg


projectile.jpg


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?
 
Last edited:
Physics news on Phys.org
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.
 
kuruman said:
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!

projectile%20final.jpg
 

Thread 'Magnitude of buoyant force in fluids of different densities'

The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?
View full post »

Similar threads

projectile motion problem with no initial velocity given
  • · Replies 3 ·
Replies
3
Views
822
Projectile motion, initial height and range given, find initial velocity
  • · Replies 8 ·
Replies
8
Views
2K
Projectile Motion Problem Involving Initial Velocity and Gravity Only
  • · Replies 11 ·
Replies
11
Views
1K
Projectile motion problem – determining initial velocity of throw
  • · Replies 3 ·
Replies
3
Views
2K
Find the height of a lamp based on the velocities of projectiles
  • · Replies 40 ·
2
Replies
40
Views
2K
Projectile Motion: initial velocity problem
  • · Replies 1 ·
Replies
1
Views
1K
Find the Initial Velocity and Launch Angle for a Particular Trajectory
  • · Replies 10 ·
Replies
10
Views
4K
seeking help finding the initial velocity of a type 3 projectile
  • · Replies 5 ·
Replies
5
Views
1K
How do you find the initial velocity of a projectile given angle/distance?
  • · Replies 3 ·
Replies
3
Views
2K
Determine initial velocity of a vertical throw
  • · Replies 11 ·
Replies
11
Views
4K