# Homework problem on projectile motion

• Kalix
In summary, projectile motion is the motion of an object in a curved path due to the influence of gravity. To solve a homework problem on projectile motion, one must understand the basic principles and use mathematical equations or diagrams. The key factors that influence projectile motion are initial velocity, launch angle, and force of gravity. The same equations can be used for all types of projectile motion problems, but some may require additional equations. To check the accuracy of an answer to a projectile motion problem, one can use equations of motion or online calculators, or ask for a review from a teacher or peer.
Kalix

## Homework Statement

Question: James and Steve have a contest to see who can kick a football further. James kicks the football at an angle up of 57 degrees, and a speed of 75m/s. Steve kicks the ball with a speed of 100m/s, at an angle up of 48 degrees? Who wins the contest?

Vix=75cos57
viy=75sin57

## Homework Equations

First, I don't really understand what variables I have and don't have. I know you can find Vix but doing 75cos57 and viy by doing 75sin57. I think I have to find time but like I said I am don't understand what variables I have or what variables I need.

Secondly, is this a two part questions? The fact that there are two different people is really confusing me.

## The Attempt at a Solution

okay here is my small attempt. I assumed that vfy=0 and vfx=0 (this doesn't seem right but I tried it anyway). Then I pulled what variables I think I had into this equation: vfx=vix+axt
With the number it looked like this 0=40.8-9.81(t)
-40.8=-9.81
t=4.15

After this I just didn't know what to do.

What I need help with: I need help clarifying the variables and knowing what variables I need
Knowing what equation to use

Hi Kalix, welcome to PF.

The problem is asking you to determine who's ball will travel furthest. So in that respect you have two separate (yet similar) problems to solve; they just have different numbers to plug in.

Each case involves a ball being kicked from ground level with some initial speed and at some initial angle, and you want to find how far the ball will travel before it hits the ground once again. In order to address this problem you first have to realize that the ball's trajectory is governed by two components: the horizontal motion, which has a constant velocity, and the vertical motion which is affected by gravitational acceleration. It's this latter motion that determines how long the ball stays in the air, while the former determines how far (horizontally) the ball will travel while it remains airborne. So, you need to write the equations that govern both of these motions and solve for the time of flight and then the horizontal distance covered in that time.

Your known values are initial speed, launch angle, and the acceleration due to gravity (in the vertical direction). Your unknowns (variables) include time, y position, and x position.

Does that help?

It helps some but I am still confused about what to do with the 2 different angles. Does this mean that I will have 2 different vix and viy values? Also do the vfy and vfx values equal 0. I assumed that in my first attempt of the problem but I wasn't sure if I was correct or not.

treat it as two separate questions and solve for the total distance kicked and whichever has the longest distance kicked, obviously wins. Furthermore, treat the x and y components seperately, so to start you off, take the y component and solve for the time because vertical motion is independent of the horizontal. Once you have your time you should be on your way.

Okay I think i am starting to understand. Just one more clarifying question: Is the distance kicked equal to x?

yes.

## 1. What is projectile motion?

Projectile motion is the motion of an object in a curved path due to the influence of gravity. It occurs when an object is launched with an initial velocity and then moves under the force of gravity.

## 2. How do I solve a homework problem on projectile motion?

To solve a homework problem on projectile motion, you need to first understand the basic principles of projectile motion, such as the equations of motion, launch angle, and initial velocity. Then, you can use these principles to set up and solve the problem using mathematical equations or diagrams.

## 3. What are the key factors that influence projectile motion?

The key factors that influence projectile motion are the initial velocity of the object, the angle at which it is launched, and the force of gravity. Other factors such as air resistance and wind can also have some influence on the motion.

## 4. Can I use the same equations for all types of projectile motion problems?

Yes, the same equations can be used for all types of projectile motion problems, as long as the initial conditions and forces are known. However, some problems may require additional equations or modifications to the existing equations.

## 5. How can I check if my answer to a projectile motion problem is correct?

You can check your answer to a projectile motion problem by using the equations of motion to calculate the final position, velocity, and time, and then comparing them to your initial values. You can also use online calculators or ask a teacher or peer to review your solution.

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