Calculating Final Position in Projectile Motion: A Case Study

In summary, the conversation revolves around finding the values of xf and yf given the initial velocity, angle, and time of a mortar fired at a mountain. The correct calculations for xf and yf are provided by using the formula for projectile motion. It is also revealed that there was a mistake in using the wrong value for time, which was corrected to get the correct answer for yf.
  • #1
NoMeGusta
15
0
I just wanted a second check on this. This is a mortar fired at a mountain to cause an avalanche. What is xf and yf given:

Vi=300 m/s
theta= 55 degrees
t = 42 secs

so I found
Vxi= 300cos(55) = 172 m/s
Vyi= 300sin(55) = 245 m/s

Xf = Xi +Vxi*t + (1/2) ax*(t^2)
= 0 +172(45) + (1/2)(0)(45^2)
= 7227 m
= 7.23 X 10^3 (this was correct w/the book)

Now for Yf
Yf = Yi +Vyi*t + (1/2) ay*(t^2)
= 0 + 245(45) + (1/2) (-9.80)*(45^2)
= 11058 - 9922
= 1136
= 1.14 X 10^3 ... book says 1.68 X 10^3

What am I doing wrong to not get Yf correct? Thanks for the help.
 
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  • #2
what's t? 42 or 45 s?
 
  • #3
Oh shoot, it is 42, but for some stupid reason I wrote 45 in finding Yf. I redid it with t=42 and I got the right answer, woohoo, thanks!
 

What is projectile motion?

Projectile motion is the motion of an object through the air or space under the influence of gravity, without any other forces acting on it.

What factors affect projectile motion?

The factors that affect projectile motion include the initial velocity, angle of launch, air resistance, and the acceleration due to gravity.

What is the formula for calculating projectile motion?

The formula for calculating projectile motion is: x = V₀tcosθ and y = V₀tsinθ - 1/2gt², where x and y are the horizontal and vertical displacement, V₀ is the initial velocity, t is the time, θ is the angle of launch, and g is the acceleration due to gravity.

What is the difference between horizontal and vertical projectile motion?

Horizontal projectile motion refers to the motion of an object along the x-axis, while vertical projectile motion refers to the motion of an object along the y-axis. In horizontal projectile motion, the object's velocity remains constant, while in vertical projectile motion, the object's velocity changes due to the influence of gravity.

How does air resistance affect projectile motion?

Air resistance can affect projectile motion by slowing down the object's velocity and altering its trajectory. This is because air resistance acts as a force in the opposite direction of the object's motion, causing it to slow down and deviate from its original path.

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