# Beginning physics question about solving for time using kinematic equations?

• JohnApplebee
In summary, the problem involves finding the height of a racket ball when it leaves the racket at a speed of 5.37 m/s and lands 2.15 m away. The solution involves using kinematic equations and solving for time, which can be done using the distance over speed formula or 2-Dimensional kinematic equations. The issue may arise if the final velocity of x is assumed to be either 0 or 5.37, and showing work may help determine the correct answer.
JohnApplebee

## Homework Statement

A racket ball is struck in such a way that it leaves the racket with a speed of 5.37 m/s in the horizontal direction. When the ball hits the court, it is a horizontal distance of 2.15 m from the racket. Find the height of the racket ball when it left the racket.

## Homework Equations

Kinematic equations

## The Attempt at a Solution

I already have the solution BUT it's because I solved for time using the formula time = distance / speed. However, I tried solving for time using the 2-Dimensional kinematic equations involving acceleration (-9.8), time, Inital velocity, etc. I plugged in all the variables except for time and my answer for time came out way wrong. So why is that? What am I doing wrong? Thanks.

And just wondering: would final velocity of x (Vx) = 0 or 5.37?

JohnApplebee said:
What am I doing wrong?
I don't know. If you show your work maybe I could say.

And just wondering: would final velocity of x (Vx) = 0 or 5.37?
If you were hard-pressed to think about it, which would you say and why?

## 1. How do I solve for time using kinematic equations?

To solve for time using kinematic equations, you will need to have at least three known values: initial velocity, final velocity, and acceleration. You will also need to know which kinematic equation to use depending on the given scenario. Once you have these values, you can plug them into the appropriate equation and solve for time.

## 2. What are the four kinematic equations?

The four kinematic equations are:
1. v = u + at (final velocity = initial velocity + acceleration x time)
2. s = ut + 1/2at² (displacement = initial velocity x time + 1/2 x acceleration x time²)
3. v² = u² + 2as (final velocity² = initial velocity² + 2 x acceleration x displacement)
4. s = (u + v)/2 x t (displacement = average velocity x time)

## 3. What is the difference between distance and displacement?

Distance is a scalar quantity that refers to the total length traveled by an object, while displacement is a vector quantity that refers to the straight-line distance between an object's initial and final position. Distance can be positive or zero, but displacement can be positive, negative, or zero depending on the direction of motion.

## 4. Can I use kinematic equations for circular motion?

No, kinematic equations are only applicable for linear motion. For circular motion, you will need to use other equations that involve angular velocity and radius instead of linear velocity and displacement.

## 5. Is there a specific order to solve for the variables in kinematic equations?

Yes, the order of solving for variables in kinematic equations is generally: first, identify the known values and unknown value to be solved for. Then, select the appropriate kinematic equation and rearrange it to solve for the unknown variable. Finally, substitute the known values into the equation and solve for the unknown variable.

Replies
3
Views
2K
Replies
18
Views
576
Replies
16
Views
2K
Replies
4
Views
1K
Replies
7
Views
2K
Replies
3
Views
2K
Replies
2
Views
2K
Replies
3
Views
2K
Replies
5
Views
3K
Replies
4
Views
1K