How to get initial and final velocity? thanks

[jamesblim168]

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

 

[jamesblim168]

up for today...

 

[jamesblim168]

up for today...

 

[voko]

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.

 

[jamesblim168]

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?

 

[HallsofIvy]

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?

 

[voko]

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?

 

[jamesblim168]

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

 

[jamesblim168]

up for today...

 

[jamesblim168]

up for today...

 

[azizlwl]

It depends on the horizontal distance of the cannon and the first wheel, and the last wheel with the safety net.

 

[jamesblim168]

how would i know? those are the only values i have... does this mean this problem cannot be solve?

 

[Jakeus314]

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?

 

[Jakeus314]

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.

 

[jamesblim168]

what do you mean? how to decide?

 

[jamesblim168]

can anyone help me solve this?

 

[jamesblim168]

would really appreciate the effort ... thanks

 

[Jakeus314]

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.

 

[azizlwl]

You can find the velocity for maximum range, the distance between the wheels.
For maximum range the angle at above first wheel is 45°.

 

[jamesblim168]

up for today...

 

[Jakeus314]

What is "up for today.." ?

 

[azizlwl]

up for today...

Can you find the velocity just above the first wheel?

 

[jamesblim168]

Can you find the velocity just above the first wheel?

no, coz i don't know how...

 

[ehild]

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

 

[jamesblim168]

so what is my initial veloctiy if my angle is 45 degress?

 

[ehild]

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

 

[jamesblim168]

what is the equation? what formula are you using to get the initial velocity?

 

[ehild]

That you have to know. What equations are there for projectile motion?

ehild

 

[jamesblim168]

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...

 

[jamesblim168]

is this the right formula for getting the initial velocity?
Vo = V - at
Vo - initial velocity
V - Velocity
a - acceleration
t - time

 

[azizlwl]

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...

1. Given range(distance first and last wheel). From this you can calculate horizontal the velocity V_x.

2. From this velocity you find the maximum height the man goes above the middle wheel assuming equally spaced wheels.

3. Add this height to the height from top of the wheel to the gun.

4. You have total height to cover with 45degree projectile

 

[voko]

What we have been saying is that you cannot calculate anything now, because the problem requires that you make certain assumptions on the arrangement. All you know is how wide the three wheels (= W) to fly over, and how high (= H) they are. But you do not know how far from the wheels the launch pad and the target net are. These unknown distances and W and H will together result in certain restrictions on the equations of motion, from which you could deduce the minimum initial velocity.

 

[jamesblim168]

where are you masters?

 

[jamesblim168]

so your saying il make assumptions so there's no wrong answer here? outcome will depend on my assumptions?

 

[jamesblim168]

can anyone solve this?