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Murder Mystery Solution using Kinematic Equations

  • #1
I'm new to this site, so let me know if I'm doing anything wrong.

Homework Statement


I have attached the original problem in a PDF file. I have to read a murder mystery story and pull information from it to plug into kinematic equations and find out who commited the murder.

Important information that I have pulled out of the story:
--No air resistance
--Each room is has a 14ft high ceiling with 2 feet between each floor.
--Bloodstains are 18ft from the entrance to the building
Victim:
1. Adam Able. 5'11. 160 lbs.

Suspects:
1. Adrianna Myers (Room 356)
2. Steven Caine (Room 852)
3. Mark Johnson (Room 1956)
4. Stanley Michaels (Room 2754)


Homework Equations


Kinematic Equations:
1x. V=Vo+at
2x. X=Xo+1/2(V+Vo)t
3x. X=Xo+Vot+1/2at^2
4x. V^2=Vo^2+2a(X-Xo)

1y. Y=Vo+at
2y. Y=Yo+1/2(V+Vo)t
3y. Y=Yo+Vot+1/2at^2
4y. V^2=Vo^2+2a(Y-Yo)

Xo & Yo = Initial Position
X & Y = Final Position
Vo = Initial Velocity
V = Final Velocity
A = Acceleration
T = time


The Attempt at a Solution


Knowing that each floor is 16ft total, I use the person's room number to find out high up the are. I know that in the end I need to figure out how high up Adam fell from and compare that to the suspects rooms to know who killed him. Note: I've also converted everything to meters

The first thing I did was solve for time using the x-axis equations.
Xo=0
X= 5.4864 m (18ft where bloodstains were)
Vo = 0 m/s
V = 2 m/s (You'll notice in the attached file that our teacher gives a hint stating that if we were in lab and pushed our partner hard, we'd find that they'd have a speed of 2 m/s)
a = ?
t = Find!
I plugged all of this into Equation 2x and got 5.864 seconds. (I believe this is wrong after going further, I'm just explaining what I did.

The second thing I did was plugged in the time to find out Yo.
Yo = Find!
Y = 0 m
Vo = 0m/s
V = ?
a = -9.81 m/s (Gravity)
t = 5.4864 s
I plugged this into Equation 3y and got 25.24 m. This is seeming way off.

I know this is long. This is a take-home problem for my exam tomorrow. I'm not asking anyone for answers. I just need help going in the right direction. This is my first physics class ever and its turning out to be way harder than I expected and I have no friends takign classes like mine.

Homework Statement





Homework Equations





The Attempt at a Solution

 

Attachments

Answers and Replies

  • #2
gneill
Mentor
20,799
2,777
For the horizontal motion, Adam's initial velocity will be about 2m/s and there will be no acceleration in the horizontal direction after he's shoved. It looks like your equation 3x would be the better choice, setting a to zero.
 

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