A falling stone takes 0.28 s to travel past a window 2.2 m...

In summary: But if downward is positive then only V0 has a negative sign in your final equation, and g ends up with a positive sign.So if downward is positive then vo has a negative sign and the stone falls faster.
  • #1
teatime95
2
0

Homework Statement


A falling stone takes 0.28 s to travel past a window 2.2 m tall.
From what height above the top of the window did the stone fall?
So from this problem I think I have these variables:
vo = ? (or 0 because falling usually indicates 0 for an initial velocity?)
yo = 0
y = 2.2m
t = 0.28s
a = -9.8m/s^2

Homework Equations


Kinematic equations:

y=yo+vo*t + 1/2*a*t^2
v^2 = v^20 + 2a(y-y0)

The Attempt at a Solution


[/B]
I originally tried to use the first equation above, and solve for vo if I assumed it was not equal to zero.
So I isolated vo and got,
vo = -2.2 + 1/2(-9.8m/s^2)(0.28s)^2 / -0.28s
vo = 9.229m/s

After which I tried to substitute that value in my second equation which also didn't give me the correct answer for height (which i think is the new yo)
My textbook gives me the final answer but not the steps that it reached to get to it.

I have included the final answer here in white ink (so highlight to read) In case anyone wants to check their work or work backwards: [COLOR=#black]2.1m [/COLOR]

I feel like my process and identifying my variables given correctly is wrong and I'm at that point where I am confusing myself repeating this question.
Guidance would greatly be appreciated,
Thank you all!
Newbie in Physics
 
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  • #2
teatime95 said:
I originally tried to use the first equation above, and solve for vo if I assumed it was not equal to zero.
So I isolated vo and got,
vo = -2.2 + 1/2(-9.8m/s^2)(0.28s)^2 / -0.28s
That's an OK method. But redo it more carefully.

teatime95 said:
yo = 0
y = 2.2m
Since the stone is falling, that final value of y must be negative.
 
  • #3
Doc Al said:
That's an OK method. But redo it more carefully.

Is my math wrong here^ am I isolating for the correct variable?

Since the stone is falling, that final value of y must be negative.

If I change 2.2 to -ve I still get the same number -9.229, and I am still unsure what I do after?
 
  • #4
teatime95 said:
If I change 2.2 to -ve I still get the same number -9.229, and I am still unsure what I do after?
I get a different value for v0.

Show what you've put into this equation:
teatime95 said:
y=yo+vo*t + 1/2*a*t^2
Don't isolate v0 yet, just show what you have for the values in that equation.
 
  • #5
Check your signs.
If downward is negative then both V0 and g have negative signs, they both end up with negative signs in your final equation for V0.
 

Related to A falling stone takes 0.28 s to travel past a window 2.2 m...

1. How can the time it takes for a falling stone to travel past a window be calculated?

The time it takes for a falling stone to travel past a window can be calculated using the formula t = √(2d/g), where t is the time, d is the distance, and g is the acceleration due to gravity (9.8 m/s²).

2. Why does the time it takes for a falling stone to travel past a window matter?

The time it takes for a falling stone to travel past a window is an important factor in understanding the motion and speed of the stone. It can also be used to calculate other variables such as the stone's initial velocity or the height from which it was dropped.

3. How is the distance from the window to the ground related to the time it takes for a falling stone to pass by?

The distance from the window to the ground is directly proportional to the time it takes for a falling stone to pass by. This means that as the distance increases, the time also increases, and vice versa.

4. Is the time taken for a falling stone to pass by a window affected by the mass or weight of the stone?

No, the time taken for a falling stone to pass by a window is not affected by the mass or weight of the stone. This is because the time is only dependent on the distance and acceleration due to gravity, not the mass or weight of the object.

5. Can the time it takes for a falling stone to pass by a window be different in different locations on Earth?

Yes, the time it takes for a falling stone to pass by a window can be different in different locations on Earth. This is because the acceleration due to gravity varies slightly in different locations, which can affect the time calculated using the formula t = √(2d/g).

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