Physics Investigation: The effect of speed on braking distance

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Physics Investigation:

The effect of speed on braking distance

Hashim Al-Hasani 11R


Speed is the travelled distance for every moment/unit of a set time. Speed, distance and time are all related with each other, shown in the following equation, which can be rearranged to find the formula of each measurement:

Speed (m/s) = Distance (m) ÷ Time(s)

The braking distance of an object is the distance it takes to slow the object down, until it is has stopped (stationary). The object will only become stationary when the driving force is being counter-forced, for example friction and air resistance.

The kinetic energy of an object is the energy it gains due to its motion. The equation for kinetic energy is:

 What factors can affect the braking distance of an object?

Well there are 3 main factors that affect the braking distance of an object:

The height from which the object is released

This can affect the braking distance as the higher the object is when it is released, the greater it’s original GPE. As the object continues downwards, its GPE decreases, and its kinetic energy increases by the same amount of gravitation potential energy lost. Yet still, the increase in kinetic energy is never exactly equal to the amount of GPE lost, as friction and air resistance (the forces acting on the object) transfer some of this energy into heat and sound.

The surface the object is travelling on

This can affect the braking as different surfaces have a varying amount of resistance force (friction.) E.g., ice is more ‘slippery’ than a rough surface because it is very smooth, and therefore exerts less friction on the object travelling on it. The friction force gradually converts the kinetic energy of the moving object into different forms of energy such as sound and heat, until the object’s kinetic energy is reduced to zero – hence why it always stops eventually. The longer it takes for the object to have its kinetic energy reduced to zero, the longer the braking distance.

The mass of the object

 This can affect an object’s breaking distance because if the mass of an object is doubled, its kinetic energy will be increased, and as a result more work will need to be done by the resisting surface to convert the object’s kinetic energy into other forms of energy in order to stop it.

In this experiment, I will be investigating the effect of a ball’s speed on its breaking distance. I will be dropping the ball from certain distances along a ramp, which is positioned at a certain height along the clamp-stand. As well as that I will also be using a carpet as I will need to slow the ball down as it travels down the ramp.  

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There are numerous methods to measure the speed of the ball as it travels from the ramp and onto the carpet. These are the two methods that I have used during the Preliminary in order to test out which is better, and why. The following table lists both its advantages and disadvantages, of the methods, and also have brief description about each one.

The table below lists the advantages and disadvantages of possible methods, and describes how they are to be carried out.

As a result of ...

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The initial discussion about the factors affecting stopping distance was very thorough and technical vocabulary was used well, eg. work, kinetic energy, etc.The equation that needs to be used is Work done = kinetic energy. Fd = 1/2 mv^2 so if F is constant, then a graph of d against v^2 should give a straight line. The data was extensive but there was less discussion about uncertainty and the graph could be plotted more effectively. 4 stars