Physics Help. Asap
Hi everyone. I need some help with some physics. Im new to this, we just started a few days ago and this is my first year taking physics. So we did an experiment last week and i need to do a write up. It wasnt really an expermiment, more observations. . So we had a car at rest then pushed it down the ramp and it started to speed up until it got off the ramp and hit the wall.
My question is, does the car undergo [b]UNIFORM ACCELERATION[/b] why or why not?
p.s. the car is moving down an inclined plane. we just let hte car go so there was no force being applied to it from us, i think.
Sorry for the grammar and spelling, it's kinda urgent
Thanks
February 21, 2012
25 Comments • Newest first
[quote=alexwee]this convinced me not to take physics next year [/quote]
Honestly, one of the most fun courses in high school.
It's a challenge, but I really enjoyed last year, and it seems like it should be good this year too.
An acceleration-time graph? Or a velocity-time graph? An acceleration-time graph would end up with units of (m/s^2)/(s) which equals... m/s^3 and as far as I know that's not a unit...
A velocity-time graph would end up with units of (m/s)/(s) which equals m/s^2, the unit of acceleration. Hmm...
@LampShadow: Lol. I'm actually pretty interested in physics right now. We just started at its pretty cool. I'm probably one of my only friends that actually took it next year. I also took advanced functions and calculus and vectors to help me with it all. Physics seems pretty fun but I also enjoy Chemistry a whole lot. Bio...not so much. Well I'm off to bed, and I should lock this thread I guess. Bleh, tommorow. Thank you so much for your help.
this convinced me not to take physics next year
[quote=bored741258963]@LampShadow: Oh we did that lol. 3 graphs. The first was position time, the next was velocity time, and the 3rd was the now infamous acceleration time graph.
We actually plotted it the way you said, and he even said this experiment will have tons of scientific data lol.
He wanted us to make the position time graph a curve, the velocity time graph a straight line, and he left the acceleration time up to us to decide/figure out.
He also told us that the tangent method that we're using is far too flawed and we won't be doing the other methods until grade 12. But thanks again for your help, I'll add you on basil .
Edit: Nvm I cant add you, basil is glitchy Ill add you as soon as its fixed. [/quote]
lol It's alright. This method of physics is really inexact and even difficult for me to think about. But it's the easiest way for people to get introduced to physics without needing to know calculus. But once you learn calculus, stuff like this will make perfect sense and it will be so easy you'll end up like me and think this way is the biggest pain ever lol
@LampShadow: Oh we did that lol. 3 graphs. The first was position time, the next was velocity time, and the 3rd was the now infamous acceleration time graph.
We actually plotted it the way you said, and he even said this experiment will have tons of scientific data lol.
He wanted us to make the position time graph a curve, the velocity time graph a straight line, and he left the acceleration time up to us to decide/figure out.
He also told us that the tangent method that we're using is far too flawed and we won't be doing the other methods until grade 12. But thanks again for your help, I'll add you on basil .
Edit: Nvm I cant add you, basil is glitchy Ill add you as soon as its fixed.
[quote=bored741258963]Omg YAY . Can I add you as a friend on basil . We're finishing kinematics in about a month.
Then we're starting
-Waves
-Forces ( I hear its the hardest)
-Energy in society
-Electricity and Magnestism
Thank you once again, kind sir [/quote]
lol np, and sure. If you want your data to be perfect (as in your chart to be represented by your data) then it's probably not going to be a perfectly straight line. I have a feeling that they want you to determine the velocity the car was moving at for each segment (which is just the distance it traveled over time, so your measured distance divided by .1 second).
And then once you have the velocities they'll probably want you to figure out the acceleration for each segment as well. You won't be able to find it for every segment, but just remember that acceleration is the change of velocity over time, so you'll need to subtract your second velocity from the first one and then divide that one by the time it took to travel between those two segments.
Once you have all of those acceleration values you could plot them and see if they form a flat line. If it's not perfect then that's fine because nothing in the real world is perfect lol (plus that's what they call experimental error). Find the average of all the acceleration values you calculated and that should give you a pretty good estimate of what the constant acceleration was
[quote=LampShadow]Well if you ever have any problems or explanations you need help with in your physics class you can send me a pm and I'd be glad to help you out. I got my degree in physics so it'd be good for both of us if I help teach you the details lol[/quote]
Omg YAY . Can I add you as a friend on basil . We're finishing kinematics in about a month.
Then we're starting
-Waves
-Forces ( I hear its the hardest)
-Energy in society
-Electricity and Magnestism
Thank you once again, kind sir
[quote=bored741258963]Not uniform. xD
OMG OMG OMG. i love you basil. Thanks for all your help, i think i have it now. Dam this is kinda hard xD. But thanks to everyone. Wish I can pay you all back, each and every one .
I'll lock this thread in a bit, but again, thank you EVERYONE <3
Oh I forgot to mention, thanks basil ![/quote]
Well if you ever have any problems or explanations you need help with in your physics class you can send me a pm and I'd be glad to help you out. I got my degree in physics so it'd be good for both of us if I help teach you the details lol
[quote=xVolcomStone]No doubt it's uniform acceleration. However, it's not uniform motion.
@above: Yeah, an acceleration-time graph will be a straight, horizontal line. A speed-time would be a straight line with a positive slope, and a distance-time graph would be curved.[/quote]
Not uniform. xD
OMG OMG OMG. i love you basil. Thanks for all your help, i think i have it now. Dam this is kinda hard xD. But thanks to everyone. Wish I can pay you all back, each and every one .
I'll lock this thread in a bit, but again, thank you EVERYONE <3
Oh I forgot to mention, thanks basil !
Edit: @LampShadow
Yea, its the data that we collected. But I think I have it now. THANK YOU SO MUCH SIR, I CAN'T EVER REPAY YOU I LOVE YOU .
@darksuitguy
I Cant use a graphing calculator for this lol, but I think I have it now, omg thanks soooooooooooooooooooooooooooooo much everyone DDDDDDDDDDD
[quote=bored741258963]I appreciate all the help on such short notice, to everyone that posted in the thread.
I should have just said the entire experiment and the steps.
So we had a ramp at school. We attached a tickertape to the back of it. We had this machine with a slip of carbon paper under it to print points that marked the ticker tape. So it did around 60 clicks per second i believe. So we let the car go down the ramp, all in under a second. Then we measured the segments on the ticker tape, each 6 spaces made 1 segment. Then we had times for the interval, .1seconds for each segment.
The size of each segment began to increase, but my 6th segment was after the car left the ramp.
The question just says, Draw an acceleration vs time graph and did the car undergo uniform acceleration. Explain.[/quote]
I did this experiment like 6 months ago. What I did was plot a displacement vs. time graph, and tried out all the regression features to see which one had an r^2 value closest to 1 (IIRC, I did exponential). Then I derived that regression equation twice, ending up with equation for the acceleration.
If you don't know calc:
1. Try out all the regression features to see which one had an r^2 value closest to 1 (the closer to 1 the r^2 value is, the better fit that equation is for the data), and save that equation to Y1.
2. nderiv(Y1,x,x) and save that as Y2 (this represents velocity)
3. nderiv(Y2,x,x) and save that as Y3 (this represents acceleration)
4. Have your calculator display only Y3. If Y3 is not a straight line, that means the car is not undergoing constant acceleration. If it is, then the car is undergoing constant acceleration.
[quote=bored741258963]I appreciate all the help on such short notice, to everyone that posted in the thread.
I should have just said the entire experiment and the steps.
So we had a ramp at school. We attached a tickertape to the back of it. We had this machine with a slip of carbon paper under it to print points that marked the ticker tape. So it did around 60 clicks per second i believe. So we let the car go down the ramp, all in under a second. Then we measured the segments on the ticker tape, each 6 spaces made 1 segment. Then we had times for the interval, .1seconds for each segment.
The size of each segment began to increase, but my 6th segment was after the car left the ramp.
The question just says, Draw an acceleration vs time graph and did the car undergo uniform acceleration. Explain.
Edit: My friend is telling me it isnt when it leaves the ramp. MY APOLOGIES EVERYONE. So it would simply have a slope of 0? Just a horizontal line parallel to the x-axis right?[/quote]
Right, the net force acting on the car as it's falling down the ramp would be constant and therefore if you were to chart it as acceleration vs time then it would be a straight line with a slope = 0. However, the net force acting on the car would not amount to 9.8 m/s^2 as some people are saying. Because the object is falling down an incline the acceleration would be lower than that.
Do they want you to figure out what the acceleration was based on your data? Because if you can figure that out then you'd just need to draw a straight line along that value for all time values
No doubt it's uniform acceleration. However, it's non-uniform motion.
@above: Yeah, an acceleration-time graph will be a straight, horizontal line. A speed-time would be a straight line with a positive slope, and a distance-time graph would be curved.
We did pretty much the exact same thing last week in Physics, but we just did it as a review thing. I'm guessing you're in Grade 11?
[quote=LampShadow]Are you charting the car's velocity or position?
This task becomes a lot more difficult if they're asking you to include the time it spent after the ramp. After the car leaves the ramp the forces acting on it change which is why the car slows down. The vector representing the normal force becomes parallel to the force of gravity, so there's no longer any force pushing it forward. So the force of friction pushing back on it wins and the car slows down.
That seems excessively complicated for something as easy as this, especially if you haven't even learned gravity yet lol. Unless they're just wanting you to graph the forces acting on it symbolically and not numerically[/quote]
I appreciate all the help on such short notice, to everyone that posted in the thread.
I should have just said the entire experiment and the steps.
So we had a ramp at school. We attached a tickertape to the back of it. We had this machine with a slip of carbon paper under it to print points that marked the ticker tape. So it did around 60 clicks per second i believe. So we let the car go down the ramp, all in under a second. Then we measured the segments on the ticker tape, each 6 spaces made 1 segment. Then we had times for the interval, .1seconds for each segment.
The size of each segment began to increase, but my 6th segment was after the car left the ramp.
The question just says, Draw an acceleration vs time graph and did the car undergo uniform acceleration. Explain.
Edit: My friend is telling me it isnt when it leaves the ramp. MY APOLOGIES EVERYONE. So it would simply have a slope of 0? Just a horizontal line parallel to the x-axis right?
[quote=bored741258963]Oh, so the line would be the average acceleration?[/quote]
Yeah acceleration would be a line with slope 0. Acceleration is constant. Velocity is increasing linearly.
[quote=bored741258963]Yea its pretty much this I guess. I mean we havent done gravity yet, thats this week, but I think you're right.
If I were to graph it, how would it look like:
-Increase in acceleration, meaning the lines goes up....
-Leaves the ramp and begins to slow down, meaning the line goes down........
So would it end up like a parabola?
I plotted hte points from the table of values, would the parabola go through the points or would it be a line of best fit for the points. Thats where im lost at lol. My teach didnt explain it and we didnt do acceleration time graphs yet.[/quote]
Are you charting the car's velocity or position?
This task becomes a lot more difficult if they're asking you to include the time it spent after the ramp. After the car leaves the ramp the forces acting on it change which is why the car slows down. The vector representing the normal force becomes parallel to the force of gravity, so there's no longer any force pushing it forward. So the force of friction pushing back on it wins and the car slows down.
That seems excessively complicated for something as easy as this, especially if you haven't even learned gravity yet lol. Unless they're just wanting you to graph the forces acting on it symbolically and not numerically
*edit: Wait, are they asking you to chart the acceleration? Because that would be really easy even accounting for what I just said
It is until it slams into the wall...
[quote=ScrambledEgg]No, acceleration is always constant, or abruptly changing. If the graph would show an increase of anything its velocity, not acceleration. And acceleration time graph would show a flat line parallel with the x axis at either the +ive or -ive end of acceleration.[/quote]
Oh, so the line would be the average acceleration?
[quote=bored741258963]Yea its pretty much this I guess. I mean we havent done gravity yet, thats this week, but I think you're right.
If I were to graph it, how would it look like:
-Increase in acceleration, meaning the lines goes up....
-Leaves the ramp and begins to slow down, meaning the line goes down........
So would it end up like a parabola?
I plotted hte points from the table of values, would the parabola go through the points or would it be a line of best fit for the points. Thats where im lost at lol. My teach didnt explain it and we didnt do acceleration time graphs yet.[/quote]
No, acceleration is always constant, or abruptly changing. If the graph would show an increase of anything its velocity, not acceleration. And acceleration time graph would show a flat line parallel with the x axis at either the +ive or -ive end of acceleration.
Well, unless the car doesn't move at all during friction, you can't REALLY achieve uniform acceleration due to air resistance, friction, etc. Unless your teacher wants you to disregard friction/air resistance, etc.
[quote=LampShadow]Right, for this really basic experiment the only force (and therefore acceleration) that they probably want you to mention is gravity. The force of gravity would be constant throughout the experiment, so the acceleration on the car would be constant.
There are a couple other forces that act on the car, such as the force you apply to push if off at the beginning and the force of friction as it slows down on the ground (and the force of it hitting the wall). But they probably only care about the force exerted by gravity while it's on the slope[/quote]
Yea its pretty much this I guess. I mean we havent done gravity yet, thats this week, but I think you're right.
If I were to graph it, how would it look like:
-Increase in acceleration, meaning the lines goes up....
-Leaves the ramp and begins to slow down, meaning the line goes down........
So would it end up like a parabola?
I plotted hte points from the table of values, would the parabola go through the points or would it be a line of best fit for the points. Thats where im lost at lol. My teach didnt explain it and we didnt do acceleration time graphs yet.
Right, for this really basic experiment the only force (and therefore acceleration) that they probably want you to mention is gravity. The force of gravity would be constant throughout the experiment, so the acceleration on the car would be constant.
There are a couple other forces that act on the car, such as the force you apply to push if off at the beginning and the force of friction as it slows down on the ground (and the force of it hitting the wall). But they probably only care about the force exerted by gravity while it's on the slope
Only acceleration (not counting the initial addition of impulse you provided) on the car as it goes down is g, which remains constant.
Unless you're going to be so precise as to count the height difference and its negligible effect on radial gravitational acceleration.
The car moves faster as it goes down the ramp, it picks up speed. But when its off the ramp and back on the floor, it slows down.
It experiences uniform acceleration on the ramp at the very least, since it is affected only by force of gravity. When it's off the ramp, acceleration due to gravity stops altogether.