# Solving Kinematics Problem: V_o & Max Height

• DeltaForce
In summary, the formula for calculating initial velocity (V<sub>o</sub>) in kinematics problems is V<sub>o</sub> = V<sub>f</sub> - at. To calculate the maximum height, determine the time it takes for the object to reach its highest point using the formula V<sub>y</sub> = V<sub>o</sub> + at, and then use the formula y = V<sub>o</sub>t + (1/2)at<sup>2</sup>. "V<sub>o</sub>" stands for initial velocity and "V<sub>f</sub>" stands for final velocity, with "V<sub>f</sub>" also
DeltaForce
Homework Statement
John climbs a tree to get a better view of the speaker at an outdoor graduation ceremony. Unfortunately, he leaves his binoculars behind. Marsha throws them up to John, but her strength is greater than her accuracy. The binoculars pass John's outstretched hand after 0.75s and again 1.28s later. How high is John?
Relevant Equations
v_o + at = v_f
v_o*t - 0.5gt^2 = y
For this problem I tried to find when the binoculars reaches the maximum height. So, (0.75 + 1.28)/2 = 1.015s. Using that information I can solve for the initial velocity. v_o = gt = 9.947 m/s.

Then using the initial velocity I can solve for the height of John using the 2nd kinematics equation.

9.947(0.75) - 0.5(9.8)(0.75^2) = 4.70m

I checked the answer and solution, but it was totally different from my answer. What did I do wrong?

DeltaForce said:
How high is John?
Obviously we need more information to answer this question. What was he smoking before climbing the tree?
For this problem I tried to find when the binoculars reaches the maximum height. So, (0.75 + 1.28)/2 = 1.015s. Using that information I can solve for the initial velocity. v_o = gt = 9.947 m/s.

Then using the initial velocity I can solve for the height of John using the 2nd kinematics equation.

9.947(0.75) - 0.5(9.8)(0.75^2) = 4.70m

I checked the answer and solution, but it was totally different from my answer. What did I do wrong?
Check the wording of the question. The 1.28s is *after* the 0.75s first cross-over time...

DeltaForce
Hahahaha, I was sitting there wringing my brain out figuring out what I did wrong. Now I see. Thank you!

berkeman
Happy to help. I try to avoid climbing trees after, well, you know...

DeltaForce

## What is the equation for solving kinematics problems for initial velocity and maximum height?

The equation used to solve kinematics problems for initial velocity (V_o) and maximum height is:
where V is the final velocity, V_o is the initial velocity, a is the acceleration, and d is the displacement.

## How do I determine the initial velocity (V_o) in a kinematics problem?

To determine the initial velocity (V_o), you need to know the final velocity, acceleration, and displacement. Then, use the equation:
where V is the final velocity, a is the acceleration, and d is the displacement.

## What is the maximum height in a kinematics problem?

The maximum height in a kinematics problem is the highest point reached by an object during its motion. It is usually represented by the variable h or y in equations.

## Can I use the same equation to solve for initial velocity and maximum height in any kinematics problem?

Yes, the same equation can be used to solve for initial velocity and maximum height in any kinematics problem as long as you have the necessary information: final velocity, acceleration, and displacement.

## What units should I use for velocity and height in kinematics problems?

Velocity is typically measured in meters per second (m/s) and height is measured in meters (m) in kinematics problems. It is important to use consistent units throughout your calculations to ensure accurate results.

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