Finding the initial velocity using quadratic

In summary, the problem involves finding Vi using the given equations and values. By substituting the values into the kinematic equation and solving for Vi, a value of 9.9m/s is obtained, but the correct answer is 17.05m/s. Therefore, there is an error in the algebraic steps used to solve for Vi.
  • #1
Rammer24
1
0

Homework Statement



I need to find Vi, knowing the following:

Δt=6/Vi cos40

Viy=Vi sin40

Δy=4m

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

Homework Equations



Quadratic: x= [-b +/- √(b^2-4ac)]/2a

Kinematic equation to be used: Δy=ViyΔt + 1/2ayΔt^2

The Attempt at a Solution



Δy=ViyΔt + 1/2ayΔt^2

4=(Vi sin40)(6/Vi cos40) -4.9(6/Vi cos40)^2

This is where I'm stuck, I don't know how to continue the problem and solve for Vi.

EDIT: I solved for Vi and got and answer of 9.9m/s, but according to my teacher, the correct answer should be 17.05m/s, so I'm definitely making a mistake somewhere in the algebra.

Thanks
 
Last edited:
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  • #2
IF you show your working it will be easy to see where you're going wrong.
 

FAQ: Finding the initial velocity using quadratic

What is the formula for finding initial velocity using quadratic?

The formula for finding initial velocity using quadratic is v0 = (xf - x0) / t + (1/2)axt, where v0 is the initial velocity, xf is the final position, x0 is the initial position, t is the time, and ax is the acceleration in the x-direction.

How is quadratic used to find initial velocity?

Quadratic is used to find initial velocity by taking into account the initial and final position, time, and acceleration. The formula involves solving a quadratic equation to determine the initial velocity.

Can initial velocity be negative when using quadratic?

Yes, initial velocity can be negative when using quadratic, as it depends on the direction of the motion. A negative initial velocity indicates that the object is moving in the opposite direction of the positive direction.

What is the significance of finding initial velocity using quadratic?

Finding initial velocity using quadratic is significant because it allows us to calculate the velocity of an object at a specific point in time, based on its initial and final position and acceleration. It is often used in physics and engineering to analyze the motion of objects.

Can initial velocity be calculated without using quadratic?

Yes, initial velocity can be calculated without using quadratic, but it may require additional information such as the object's speed, direction of motion, and angle of launch. Using quadratic provides a more accurate and comprehensive method for calculating initial velocity.

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