How to get initial and final velocity? thanks

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Homework Help Overview

The discussion revolves around a physics problem involving projectile motion, specifically analyzing the trajectory of a human cannonball who must soar over three ferris wheels of a certain height while covering a specified horizontal distance. The problem requires determining the initial velocity needed for the cannonball to safely land on a net or, alternatively, the velocity upon striking the ground if the net is missed.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the conditions necessary for the cannonball's trajectory, questioning the assumptions regarding the launch angle and distances involved. Some suggest that the initial velocity should be minimal for the stunt to be successful, while others express confusion about the equations and methods to apply.

Discussion Status

The discussion is ongoing, with participants offering various insights and questioning the assumptions needed to approach the problem. Some have provided guidance on considering the arrangement of the ferris wheels and the launch pad, while others have pointed out the need for a drawing to clarify the setup. There is no consensus on a specific solution yet, as participants are still exploring different interpretations and approaches.

Contextual Notes

Participants note that the problem lacks certain values and conditions, which complicates finding a definitive solution. The need for assumptions about the distances and angles involved is emphasized, as these will significantly affect the calculations of initial velocity and trajectory.

jamesblim168
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Homework Statement


a human cannonball in 1940 soared over three ferris wheels, each 18 meters high covering a horizontal distance of 10.63 meters. Assuming that the point of projection is 2.50 meters above the ground and that he landed safely on a net placed at the same level, find his initial velocity. Assuming that he missed the net and landed on the ground, with what velocity will he strike the ground?


Homework Equations





The Attempt at a Solution

 
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If no more conditions are given, it seems that the problem requires that you find an optimal setup for the stunt, optimal in the sense that the initial velocity is minimal.
 
voko said:
If no more conditions are given, it seems that the problem requires that you find an optimal setup for the stunt, optimal in the sense that the initial velocity is minimal.

i don't understand how... can you teach me how?
 
You have made no attempt at all, not even citing equations that might be relevant. Are you saying that you are taking a course in which this was given as an exercise and have learned nothing about this?
 
jamesblim168 said:
i don't understand how... can you teach me how?

Imagine it is you who will be fired from a cannon in order to fly over three ferris wheels. You are in full control of the arrangement. How would you approach the problem?
 
1. Homework Statement
a human cannonball in 1940 soared over three ferris wheels, each 18 meters high covering a horizontal distance of 10.63 meters. Assuming that the point of projection is 2.50 meters above the ground and that he landed safely on a net placed at the same level, find his initial velocity. Assuming that he missed the net and landed on the ground, with what velocity will he strike the ground?


2. Homework Equations
my problem i don't know what equation il use... coz there so many missing values
is the initial velocity is 0?3. The Attempt at a Solution
this is what i did, i know its not right i hjope you guys could help me out...
“Y=Viy * t + 0.5 * Ay * t^2 “ to solve for time
-20.50m = (0 m/s) * t + 0.5 (-9.8 m/s/s) * t^2
-20.50m = (-4.9 m/s/s) * t^2
4.1s^2 = t^2
(TIME) T= 2.02s

Answer:
Problem 1:Initial velocity is 0

Problem 2: Assuming that he missed the net and landed on the ground, with what velocity will he strike the ground?

V= distance/time
V=10.63/2.02s
V=5.26m/s
 
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  • #10
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  • #11
It depends on the horizontal distance of the cannon and the first wheel, and the last wheel with the safety net.
 
  • #12
how would i know? those are the only values i have... does this mean this problem cannot be solve?
 
  • #13
An initial velocity of zero makes no sense. He wouldn't go anywhere. Can you decide where he might have to be at some point in space? Like as he approaches the first wheel?
 
  • #14
jamesblim168 said:
how would i know? those are the only values i have... does this mean this problem cannot be solve?

You may need to make an assumption about the placement of the first Ferris wheel and its distance from the cannon.
 
  • #15
what do you mean? how to decide?
 
  • #16
can anyone help me solve this?
 
  • #17
would really appreciate the effort ... thanks
 
  • #18
Is a drawing included? The orientation and position of the wheels will be important. If no drawing is included you will need to start the problem making an assumption about where the wheels are.
 
  • #19
You can find the velocity for maximum range, the distance between the wheels.
For maximum range the angle at above first wheel is 45°.
 
  • #20
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  • #21
What is "up for today.." ?
 
  • #22
jamesblim168 said:
up for today...

Can you find the velocity just above the first wheel?
 
  • #23
azizlwl said:
Can you find the velocity just above the first wheel?

no, coz i don't know how...:cry:
 
  • #24
Read about "projectile motion". The man moves both in horizontal and vertical direction. There is an equation for the x and y coordinates of the trajectory.
The projectile has to fly over the three ferris wheels, 18 m high and with distance 10.63 m between the first and last ones. The man had to be at least 18 m high above the ground at the place both of the first and last wheels.
Make a drawing to show the launch place, the wheels and the trajectory of the human cannonball.
You certainly learned that you get the maximum distance if you launch a projectile at 45 degrees. The human projectile certainly used that launch angle.

ehild
 

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  • #25
so what is my initial veloctiy if my angle is 45 degress?
 
  • #26
You have to find out both the initial velocity and the distance of launch place from the first wheel.
I attached a figure to my previous post, look at it.

What is the equation between the x and y coordinates of the projectile?

ehild
 
  • #27
what is the equation? what formula are you using to get the initial velocity?
 
  • #28
That you have to know. What equations are there for projectile motion?

ehild
 
  • #29
but i still have to get the time for me to calculate initial velocity right? then how can i get the time? why is this sooo confusing... sorry guys...
 
  • #30
is this the right formula for getting the initial velocity?
Vo = V - at
Vo - initial velocity
V - Velocity
a - acceleration
t - time
 

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