Finding initial velocity and time Please

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Homework Help Overview

The discussion revolves around a physics problem involving projectile motion, specifically calculating the initial velocity and time of flight for a missile aimed at a target 650 km away, launched at an angle of 20 degrees. Participants are exploring the necessary equations and concepts related to kinematics to solve the problem.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • Participants discuss the use of kinematic equations and the need to break down the velocity into x and y components. There is uncertainty about which equations to apply and how to relate the variables involved, particularly time and displacement.

Discussion Status

The discussion is active, with participants providing guidance on how to set up equations for both the vertical and horizontal motions. There is a recognition that two equations can be formed with two unknowns, leading to a solvable system. However, some participants express confusion about combining the equations and isolating variables.

Contextual Notes

Participants note the assumption that the missile follows a parabolic trajectory and that the only force acting on it after launch is gravity. There is also mention of the need to clarify the acceleration in both the x and y directions, with a focus on understanding the implications of constant acceleration and constant velocity.

  • #31


or with the formula u told me to use, would be:
t = (650 x 10^3) / 3157 = 206 secs

Remember x=v_x t. You entered the total speed, but instead you need to enter v_x=v cos(20). That's why you get a different answer.
 
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  • #32


so which is the correct way to do it?
and what would u advise me to put as my final answer?
 
  • #33


Picking either equations will do, however always pick the easiest to minimize the errors. Secondly for optimal accuracy don't calculate the cos/sin then round them and then use them in further calculation. Just keep them as cos/sin. Same for the other variables if you do that you get the following answers.

v=3149.61 m/s
t=219.619 s

You see that rounding constantly during the calculation introduces errors.
 
  • #34


thank you so much for all your time, help, and patience![/color]
 

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