Help with accelration due to gravity experiment

In summary, the conversation discusses a science project measuring g using the freefall method and intervals of 0.1m. Uncertainties, particularly reaction time, are causing confusion. Suggestions are given for improving the accuracy of measurements, including using Galileo's method from 400 years ago. It is noted that any experiment aiming to find the overall uncertainty in g must include a discussion of the methods and uncertainties involved in measuring time and distance.
  • #1
keil
4
0
Hey, I'm doing a science project thing, and I'm measuring g. One method was freefall, I got times of

0.53
0.55
0.57
0.60
0.63
0.65
0.66
0.67
0.68
0.70

For distances of 0.1m intervals, starting at 1.5m, and ending at 2.4m However, uncertainties are confusing me, reaction time I'm taking as 0.5s, so there's uncertainty of between 94% and 71%, depending of course on the time, anyhoo, to calculate g you use 2s/t squared, so you double uncertainty, and combine them, and it's really confusing, so can anyone help?

(i'm aware this post sort of lacks clarity, so if you need me to explain anyu bit again please ask)

Thanks in advannce for help.
 
Physics news on Phys.org
  • #2
oh, and I need to find overall uncertainty in g, sorry, forgot that bit.
 
  • #3
keil,

If your reaction time is really 0.5 seconds, then it's not an uncertainty; it's a systematic error that has to be subtracted from each of your measured times. But I doubt that the error is anywhere near half a second. Reaction time is the time it would take you to stop your clock after seeing or hearing something that you had no way of anticipating.

Imagine doing the experiment with your eyes closed. You drop the ball and start the clock at the same time (you should be able to make those pretty close to simultaneous). Then when you hear the ball hit, you stop the watch. The difference between the time when you hear the ball hit and when you actually stop the watch is your reaction time. And that might be around half a second. But when you're watching the ball fall, you can do a lot better. Make five or ten measurements of time for each of your heights. The variation in each set of results gives you the uncertainty in the time for that height.

By the way, around 400 years ago, Galileo was the first person to do this kind of experiment. He had the same problem you're having getting accurate values for time (actually he had it a lot worse than you do, because all he had for measuring time was a pendulum!). He invented a very ingenious way to solve the problem that you could probably use. See if you can find what it was with a google.com search on Galileo.
 
  • #4
Welcome to Physics Forums keil!

How did you measure the times? the distances?

Any experiment which has an objective of finding "the overall uncertainty in g" will need to include a discussion of the means of measuring time and distance, and the uncertainties of those measurements.
 

What is acceleration due to gravity?

Acceleration due to gravity is a physical constant that represents the rate at which an object falls towards the center of the Earth. It is typically denoted by the symbol "g" and has a value of 9.8 meters per second squared (m/s²). This means that for every second an object falls, its velocity increases by 9.8 meters per second.

How can I measure acceleration due to gravity?

One way to measure acceleration due to gravity is by using a simple pendulum. By measuring the period of oscillation of the pendulum and using the equation T = 2π√(L/g), where T is the period, L is the length of the pendulum, and g is acceleration due to gravity, you can calculate the value of g. Another method is by dropping an object from a known height and measuring the time it takes to reach the ground, using the equation d = 1/2gt², where d is the distance, t is the time, and g is acceleration due to gravity.

What factors affect the acceleration due to gravity?

The main factor that affects acceleration due to gravity is the mass of the object. The more massive an object is, the greater its gravitational force and therefore the higher its acceleration due to gravity. The distance from the center of the Earth also plays a role, as objects closer to the Earth's surface experience a stronger gravitational force and thus a higher acceleration due to gravity. Other factors such as air resistance and the rotation of the Earth can also have a minor impact.

Why is acceleration due to gravity important?

Acceleration due to gravity is important because it is a fundamental constant in physics that helps us understand the behavior of objects on Earth. It is used in a wide range of fields, from engineering and construction to astronomy and space exploration. Understanding acceleration due to gravity also allows us to explain phenomena such as free fall, projectile motion, and the motion of planets around the Sun.

Can the value of acceleration due to gravity change?

While the value of acceleration due to gravity is typically considered constant, it can vary slightly depending on location. This is because gravity is affected by factors such as the Earth's shape and density, as well as the presence of other large objects nearby. Additionally, the value of g can change with altitude and latitude due to the Earth's rotation and the centrifugal force it creates. However, these variations are very small and do not significantly impact most experiments or real-world applications of acceleration due to gravity.

Similar threads

  • Introductory Physics Homework Help
Replies
2
Views
3K
  • Astronomy and Astrophysics
Replies
2
Views
880
  • Introductory Physics Homework Help
Replies
4
Views
38K
Back
Top