Calculate Time for Projectile w/ 12° Incline

[kLPantera]

Homework Statement

My group and I had a lab, and we need to calculate time in order to proceed with the lab.

We need to calculate how far and how long the projectile will travel using the degree we are given to hit the target that will be placed X meters using our calculations.

We have a cannon tilted 12 degrees
Delta Y: 0.87m above ground (so -0.87)
V initial x: 4.02 m/s (calculated using cos)
V initial y: 0.85 m/s (calculated using sin)
Muzzle Velocity: 4.11 m/s
t = ?

Homework Equations

However I am not sure whether or not I used the right values for the equation, to find the amount of time it will travel from the cannon to the target.

The Attempt at a Solution

Y = V_it + (1/2)at²
-0.87=4.11t + (1/2)(-9.8)t²
0 = -4.9t² +4.11t + 0.87

The next step I used the quadratic formula to find the possible values for t. However for V_i do I use 4.11 or 4.02? Since 4.11 m/s is the muzzle velocity and 4.02 m/s is the initial velocity in the x direction.

 

[rl.bhat]

In the given formula you have to v initial y.

 

[kLPantera]

v initial y...? what?

 

[zgozvrm]

In the given formula you have to v initial y.

What rl.bhat is saying, is that in your formula (Y=V_it + (1/2)at^2[/tex]), since you are looking for the distance in the Y direction (D_y[/tex]), you should be looking for V_{iy}[/tex] (the initial velocity in the Y direction).

 

[kLPantera]

Oh ok thanks all.