Simple Projectile Motion Problem. Unknown initial speed.

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Homework Help Overview

The discussion revolves around a projectile motion problem where a ball is thrown at an angle of 30 degrees with an unknown initial speed. The goal is to determine the speed required for the ball to land 3 meters away from the launch point, with both initial and final heights being 0 meters.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to calculate the initial speed using kinematic equations but expresses uncertainty about the validity of their approach. Some participants question the reasoning behind the original poster's feelings of doubt and suggest verifying the calculations.

Discussion Status

The discussion is ongoing, with participants exploring the original poster's calculations and encouraging verification of the results. There is an emphasis on checking the strategy used to arrive at the initial speed, but no consensus has been reached regarding the correctness of the solution.

Contextual Notes

Participants note the importance of understanding the kinematic equations and the implications of the problem setup, including the angle of launch and the distance to be covered. There is an acknowledgment of the need for further exploration of the time of flight in relation to the initial velocity.

TruthSeaker15
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A ball is thrown at an unknown speed at an angle of 30 degrees.

The initial and final height from the ground is 0 meters.

What speed should the ball be launched at in order for it to land on the ground 3 meters from the launch point?


Here is what I tried:

http://farm6.staticflickr.com/5548/10665499106_3549cac0cc_o.jpg

I got 5.829 m/s but I feel this is wrong.
 
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"I feel this is wrong" is OK, but then you should do something about your feeling. Why does that feel wrong? Can you check your solution somehow? In the end, we are not magicians here, you can do whatever we can.
 
It feels wrong because I'm not sure if my strategy was legitimate. I tried to check it, but I didn't really know how to.
 
You have used the kinematic equations to find the initial velocity. Now that you have the initial velocity, you can also find the time; then substitute the time and the initial velocity back into the equations and see whether you get what you should.
 

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