An investigation into factors that effect the braking distance of a trolley

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An investigation into factors that effect the braking distance of a trolley.

(1) Skill Area P: Planning Experimental Procedures

Aim:

To investigate factors, which determine the stopping distance of a trolley accelerating down a ramp.

When a car is situated at the top of ramp, we say it has gravitational potential energy. When the car travels down the ramp, the gravitational potential energy is transferred to kinetic energy, so therefore

KE= ½mv²  

(Kinetic Energy = ½ x mass x velocity²)

At the bottom of the ramp work has to be done in order to stop the car; so therefore

Work Done = Braking Force x Braking Distance

Also, this must be equivalent to the original energy of the car, which was gravitational potential. So, assuming no other loss of energy:

Potential Energy = Kinetic Energy = Work Done

Background Information:   

When a mass is raised and there are no opposing forces acting upon it, the potential energy gained will be converted to kinetic energy as it falls back to earth due to the gravitational pull. The potential energy gained must therefore be equal to the kinetic energy it produces due to the theory of energy conservation - energy cannot be created or destroyed. This is shown in the formula: -

 

PE = mgh

 

From this formula we can assume that the height of the trolley will have a direct correlation to its stopping distance. It is logical to predict that if the height of the trolley (h) is increased the potential energy it gains will be larger and consequently the kinetic energy it is converted to will be greater. Therefore it is logical to predict that the greater the height of the trolley the greater the stopping distance will be. Because the kinetic energy will be greater as height increases so will the forces required to stop the motion and as the force used to stop the trolley is kept constant the stopping distance will increase.

Diagram:

Hypothesis:

I know that the speed and braking distance vary when the height of the ramp height is altered so I plan to investigate the relationship and I predict that as the height of the ramp increases so will the braking distance and velocity. This is because if the ramp was at 0° to the bench then the forces would be balanced and therefore no movement takes place whereas if it is at a much greater height the balance forces become unbalanced. We could link this to Newton’s second law, which suggests if there is an unbalanced force, then the object will accelerate in that direction. Therefore, as the height the ramp is increased, Gravitational Potential Energy is increased and hence more Kinetic Energy would be present and as a result the car would have a bigger Braking Distance. This is because the more Kinetic Energy the car has then the further the car will travel.

I need to undertake some Preliminary work to make a series of predicted braking distances. There are numerous ways in which to test this prediction. To test it, I will record the stopping distance of the trolley at different heights up a ramp, then, to check if the stopping distance is proportional to the distance of the trolley up the ramp, I will plot a graph. This graph, if the prediction is correct, will be an straight line.

Preliminary Work:

The variables, which could affect the acceleration of a trolley down a ramp, are:

The mass of the trolley, - (the size of the trolley), if the same force acts on a bigger object it will accelerate less than that force on a smaller object.

The continuous force, - (how much the object is pushed), the bigger the push or force, the bigger the acceleration.

The gradient of the slope, - (the height of the slope that the object moves down), the bigger the gradient, the bigger the acceleration will be as the object travels down it, because less friction acts against an object which travels down a steeper slope and friction reduces the acceleration of an object.

The variable, which I have chosen to investigate, is the gradient of the slope. I think that out of all the variables, this could be measured easily and changed accurately, ensuring a wide variety of reliable data. I predict that as I increase the height of the slope (or the angle between the floor and the ramp), the acceleration will increase, due to a more direct force from gravity caused by less friction on a steeper slope.

A preliminary experiment must be carried out in order to determine the appropriate heights that should be used for various measurements to replicate braking force. To find the most suitable height for this particular experiment the trolley will be used without additional mass i.e. the mass of the trolley will be kept constant. If the trolley mass is kept constant we can easily see what effect the height is having on stopping distance. This is vital in order to carry out an experiment where it is possible to make the most accurate observations and where a wide range of results is easily recorded.

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By altering a the heights of the ramps and releasing the trolley down the ramp we get an indication of how far the trolley is likely to travel and we can see if there is a link between the height of the ramp and the stopping distance of the trolley. We experimented with 9 different ramps ranging from 5 – 45cm.

To get my results, I will use a ramp height of 5cm throughout my first Preliminary work and the trolley with the same mass. I will let the car travel down the ramp 3 times; each time I ...

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