Javelin throw, find time it takes for angle one to change to angle two

In summary, the javelin is launched at a speed of 27 m/s at an angle of 34° above the horizontal. As it travels upward, the angle decreases and the time required for the angle to reduce from 34° to 15° can be calculated using the equation t=((cos34 deg)*(27m/s)*(sec15deg)-27m/s)/-9.8m/s^2. The final time is approximately 0.390s.
  • #1
pinoypride333
2
0
1. Homework Statement
In the javelin throw at a track-and-field event, the javelin is launched at a speed of 27 m/s at an angle of 34° above the horizontal. As the javelin travels upward, its velocity points above the horizontal at an angle that decreases as time passes. How much time is required for the angle to be reduced from 34° at launch to 15°?

Vi=27m/s
ay (g) = -9.8m/s^2
ax = 0m/s^2

2. Homework Equations
Vaverage=(Vf+Vi)/2=d/t
a=(Vf-Vi)/t

My teacher wants us to derive all other equations from this...I understand the why part of physics, it's just the "how" that I have trouble with. My teacher calls it "mathematical massaging". Also, he combines all of his equations into one giant one so that he only has to input his numbers once, no need to press "enter" several times. If you could please demonstrate how to "massage" the given equations and combine them into the larger final equation, that would be a great help.

3. The Attempt at a Solution
t=(Vf-Vi)/a
t=((cos34 deg)*(27m/s)*(sec15deg)-27m/s)/-9.8m/s^2
The reason I multiply cos34*27m/s*sec15 is so that I can find the final Velocity (cos34*27m/s gives the x component which is constant since there is no acceleration/deceleration)
my answer is .390s which isn't right (ignore sig figs, my teacher turned them off on WA for this assignment)
 
Last edited:
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  • #2
never mind...I found out the answer...
 
  • #3


I would approach this problem by first identifying the known and unknown variables. In this case, the known variables are the initial velocity (Vi=27m/s), the acceleration in the y-direction (ay=-9.8m/s^2), and the initial angle (θ1=34°). The unknown variable is the time it takes for the angle to change from 34° to 15°.

Next, I would use the equations of motion to derive an equation that relates the known and unknown variables. In this case, we can use the equation for the x-component of velocity (Vx=Vicosθ) and the equation for the y-component of acceleration (ay=g) to find the time it takes for the angle to change.

Vx=Vicosθ
Vx=27m/s*cos34°
Vx=22.35m/s

ay=g
ay=-9.8m/s^2

Using the equation a=(Vf-Vi)/t, we can rearrange it to solve for t:

t=(Vf-Vi)/a
t=(Vx-Vi)/ay
t=(22.35m/s-27m/s)/-9.8m/s^2
t=0.51s

Therefore, it takes 0.51 seconds for the angle to change from 34° to 15°. This approach uses the basic principles of physics and does not require "mathematical massaging" or combining multiple equations. However, if your teacher wants you to use a specific method, it would be best to follow their instructions.
 

1. What is the purpose of measuring the change in angle during a javelin throw?

The change in angle during a javelin throw is measured to understand the trajectory and distance of the throw. It can also help in identifying any errors in technique that can be corrected to improve performance.

2. How is the change in angle during a javelin throw measured?

The change in angle is measured using a protractor or an angle measuring device. The angle is measured at the point of release and again at the point of landing to calculate the change in angle.

3. What factors can affect the change in angle during a javelin throw?

The change in angle during a javelin throw can be affected by factors such as wind, release point, grip, throwing technique, and the condition of the javelin. These factors can impact the trajectory and distance of the throw.

4. How does the change in angle affect the distance of a javelin throw?

The change in angle directly affects the distance of a javelin throw. A larger change in angle results in a higher trajectory, leading to a longer distance. A smaller change in angle can cause the javelin to fall short of the desired distance.

5. What is the relationship between the change in angle and the time it takes for angle one to change to angle two?

The time it takes for angle one to change to angle two during a javelin throw is directly proportional to the change in angle. This means that a larger change in angle will take longer to occur, while a smaller change in angle will happen more quickly.

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