Does weight affect the speed a ball rolls down a ramp?

Question

I am doing a science experiment and am trying to find out if mass affects the speed rolls down a ramp. The ramp is balanced at 15cm high and is 120cm long. The three balls are of different size and they weigh : 54.5g, 25.5g and 5.6g

my results show that mass does affect it but Galileo's theory says it doesn't so im slightly confused, any help would be greatly appreciated.

Answer 1

Designing good experiments and controlling for variables is difficult.



You are correct that the theoretical acceleration of balls down a ramp is independent of mass. But there are many things that could modify the theoretical acceleration.



A track that isn't perfectly smooth or other imperfections and air resistance have non-linear effects. They'll slow down the less massive sphere more than the larger spheres.



Also, you'll have errors in your ability to release and time the spheres. Have you performed enough experiments that you have a good idea of the error that you're generating?

Answer 2

There are two opposing forces along the surface of the ramp that determine the net force and, thus, the acceleration of the ball down the ramp. The first is the motivating force w = W sin(theta), where W = mg is the weight of the ball and theta is the incline angle of the ramp.



The second is the retardation force from friction f = kN = kW cos(theta) = kmg cos(theta); where k is the coefficient of rolling friction. Put the two together and you have the net force:



F = ma = w - f = mg(sin(theta) - k cos(theta); so the acceleration down the ramp is:



a = g(sin(theta) - k cos(theta)).



And there you are sports fans. Neither m, the mass of the ball, nor W, the weight of the ball make a difference in the rate of acceleration down the ramp.



Your errors are typical of faulty experimentation. As the three balls are different size, they probably lie along the ramp's guide rail and touch the sides of the railing in different spots. This means the k, the coefficient, of rolling friction for the three balls is probably different (I'm guessing larger for the bigger balls). And as you can see from a = g(sin(theta) - k cos(theta)) a large k means a slower acceleration and consequent speed at the bottom of the ramp.



So if the bigger balls are the slower balls, that's probably where the error in experimentation is.



To block out that possibility of different k's for each ball, use just one ball, but use a ball that you can change the weight of by adding or subtracting some mass. That will keep the size and material of the ball the same for each roll down the ramp. And that should result in the same k for each trial.



WARNING. That one experimental ball will be hollow; so you can fill it with something. But make sure it's completely filled with whatever you put into it. Otherwise the ball will not roll smoothly down the ramp as its innards slosh about. So fill it with air (empty), sand, and water, for example, to the brim. That will give the ball light, medium, and heavy weight/mass that will not slosh about.



Weigh the ball each test and calculate the mass m = W/g.

Answer 3

Rolling down a ramp is different from leaving from certain height.If we leave at certain height then i goes with 9.8 m/s^2 acceleration.But if you leave down a ramp then weight 'mg' is balanced by normal reaction but it's resolved vector mg cos A gives some extra force for that ball to move.So the more the mass is the faster it reaches the end of the ramp.It's just simple if you know the concept vectors.

Answer 4

mass and weight are two very different things. if you want a good grade or whatever you will have to get your facts straight.

Answer 5

It does because the heavier the ball is the faster it will roll.