Stone projectile motion problem

In summary, the problem is asking for the angle of projection of a stone that is initially launched from ground level at 80 m/s and reaches a speed of 60 m/s at its highest point. The correct angle of projection is 38.9 degrees, which can be found using the formula v0x = v0 * cos(theta) where v0x is the horizontal velocity and v0 is the initial velocity. This formula is derived from the fact that at the highest point, the velocity in the y direction is zero and the velocity in the x direction is the total velocity. It is important to note that in this problem, wind resistance is neglected.
  • #1
FocusedWolf
81
0
A stone is projected from ground level at 80 m/s. Its speed when it reaches its highest point is 60 m/s.

Find the angle of its projection. Answer in units of degrees.

Lost count how many times i tried to get this one right.
 
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  • #2
Post your working, so we can show you where you've gone wrong.
 
  • #3
OMG! i did it...it was my calculators fault! can't believe this.

here try this if you have a ti-89 (set mode to degrees)
(note the real values of the problem were 56m/s and 72m/s)

solve(56 = 72 * cos(x), x)

the answer it gives is weird

x = 360. * ((weird symbole)n8 + .108173447969) or x = 360. * ((weird symbole)n8 - .108173447969)

everything in my work made sense so i tried to do that manually:

56/72 = 72/72 * cos(x)
.77778 = cos(x)
cos-1(.77778) = x
x = 38.9


Now the weird thing...putting this in calculator backwards with the value i determiend for theta:

72 * cos(38.9) gets me 56! Freekin modern technology :yuck: lol

o yea if anyone else wants to know how to do this problem, remember that in problems they neglect wind resistence the horizontal velocity is constant...so at the projectiles heighest point its velocity in the y direction is zero, so the velocity in the x direction is its total velocity...so now you have v0x...and they gave v0 so the formula v0x = v0 * cos(theta) will get you theta...i just figured this out now because i wanted to organize my messed up attempts for posting :P
 
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1. What is a stone projectile motion problem?

A stone projectile motion problem is a type of physics problem that involves calculating the motion of a stone that is thrown or projected into the air. This type of problem typically involves factors such as the initial velocity, angle of projection, and gravitational force.

2. What is the formula for calculating the distance traveled by a stone in projectile motion?

The formula for calculating the distance traveled by a stone in projectile motion is d = v0t + ½at2, where d is the distance traveled, v0 is the initial velocity, t is the time, and a is the acceleration due to gravity.

3. How does air resistance affect the motion of a stone in projectile motion?

Air resistance can affect the motion of a stone in projectile motion by slowing down its velocity and altering its trajectory. This is because air resistance creates a force in the opposite direction of the stone's motion, known as drag force.

4. What is the maximum height reached by a stone in projectile motion?

The maximum height reached by a stone in projectile motion is determined by the initial velocity and the angle of projection. The formula for calculating this height is h = (v02sin2θ)/2g, where h is the maximum height, v0 is the initial velocity, θ is the angle of projection, and g is the acceleration due to gravity.

5. How can the range of a stone in projectile motion be increased?

The range of a stone in projectile motion can be increased by increasing the initial velocity or by changing the angle of projection. Additionally, reducing air resistance by using a more aerodynamic shape can also increase the range.

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