Inclined Plane Experiment Help!

[Thorium]

I am doing an experiment on inclined planes in which I have to investigate the relationship between the angle of inclination and the cart's acceleration down the plane. I used a ~100g cart made of metal, 1.5 m block of wood as the inclined plane, and a phone app to measure the time accurately.

I put the data together and did some kinematics calculation (x=ut+1/2at^2) to find the acceleration from 10 degrees to 70 degrees. I noticed that there is a smooth pattern and the acceleration is very close to gsin(theta) for 10 and 20 degrees. But it is more than gsin(theta) when we go more than 20 degrees. It even goes over 9.8 m/s^2 at angles of 60 and 70 degrees.

I am pretty sure the time was measured accurate enough, because as I said, I used an app. I was expecting the acceleration to be slightly less because of friction. So Please help me know what is really going on.

[mark_alec]

The acceleration should not be higher than 9.8 m/s^2. Double check that you have the correct data (for time and distance).

[Thorium]

Me and my group all did the calculations individually, and got same results. So I am quite sure the results are correct. What would be a possible reason for getting high accelerations?

[Stevensmay]

The reason Mark asked to check was that short of you pushing the object down the plane with your hand, it is impossible to get values greater than 9.8m/s^2. (Assuming you don't live in some area with abnormal gravity)

I'm inclined to think that the way you measured the time was were the inaccuracies came in. Were you just pressing a button on your phone when you released the object and when it reached the bottom?

[RKTR]

the time needed for reaction ? as time is measured in seconds , a small difference can cause a big change in your final result

[Thorium]

The reason Mark asked to check was that short of you pushing the object down the plane with your hand, it is impossible to get values greater than 9.8m/s^2. (Assuming you don't live in some area with abnormal gravity)

I'm inclined to think that the way you measured the time was were the inaccuracies came in. Were you just pressing a button on your phone when you released the object and when it reached the bottom?

the time needed for reaction? as time is measured in seconds , a small difference can cause a big change in your final result

I used this app called "Uart Golf" that consists of a camera that measures the time to the nearest 2 d.p.. So we recorded the motion and  determined the time correct to 2 decimal places using the playback (While it was in slow motion).

By the way, a friend of mine told me that for the high angles, the cart tends to roll and slide down the plane simultaneously. So this might contribute to more acceleration. But I don't think so, because this should still add up to give the value of gsin(theta) only, as there is not other force acting.

[BigAl]

If I remember correctly there is a software which analyses the motion of an object from the video...Try that software...


On the other hand, remember is acting on the object along the horizontal axis with respect to the plane. So as you increase inclination acceleration approaches Is the object sliding or rolling? Make sure it has no wheels otherwise things get a bit complicated.