Reflections 2: Experimental Design

 As a scientist, we tend to have many questions about our environment. To answer these questions, we naturally create experiments to test our hypothesis and see if it holds true. However, creating an experiment is not a simple task. There are necessary precautions we must take to make sure that there are no extenuating circumstances that may not produce desirable or accurate results.

This week we were tasked with the challenge of designing an experiment that will help us measure velocity. The materials we had are a ramp, a ruler, an IOLab apparatus, the IOLab program and the LoggerPro program. From this we wanted to see what affects velocity. We first started moving the wheel back and forth. We tested how velocity interacted in respect to time and displacement and compared our result. We had noticed that the more force you applied to the cart, the higher the oscillation wave's amplitude would be. Early on, we removed the need to use applied force from a human since the applied force could not be controlled. We had no method of applying a constant force or measuring it so we would get numerical values of force to explain the corresponding numerical value to velocity. Thus, we used a ramp. This eliminates the uncertainty that comes with applying an unmeasured force. By using gravitational velocity, we simply only had to release a cart from a certain height allowing a constant gravitational acceleration cause the cart's movement's down the ramp. Once we had a clear idea of how the experiment would be administered, we had to chose our variables. This are the variables we chose:

Dependent: Max Velocity

Independent: Height of Ramp

Control: Initial velocity, Medium of Ramp, Length of Ramp, Time, Cart, Release Point, Coordinate Plane and Reference Frame

The dependent variable is the effect. The reason why the dependent variable is velocity is because that is the direct variable being effected by this experiment. The velocity is dependent on the height of the ramp.

The independent variable(the cause) effects the dependent variable.The independent variable in this experiment is the height of the ramp. This is the variable we are manipulating to see how different heights effect the different results of velocity. 

The controls are the variable kept the same throughout each trial in order to prevent faulty data. 

• The initial velocity will be kept at zero for the reason we mentioned earlier. We have no way of measuring an applied velocity so we control the initial velocity to be zero each time. 
• We keep the medium of the ramp constant because we do not want a frictional force to effect the dependent variable (this could be changed to be an independent variable for another experiment to see the effects of friction on velocity but, in our case, we want to test the effects of height on velocity on the cart.) 
• We want to keep the length of the ramp constant since we don't want to test the length of ramp and its effects on velocity.
• We want to control the time it takes for the experiment to run for ease of data collecting using the IOLab 
• We want to control the cart because using different carts in the experiment can fluctuate velocity. Some carts weight more than some other carts which can or cannot affect velocity. However, we want to remove that uncertainty.
• We want to control the release point of the cart. If we were to release the cart at the middle of the ramp, that would be difficult to measure the height at which the cart is released. We set the top of the ramp to be the (0, h) coordinate or our release point.
• The coordinates are also important. I released my cart with one wheel at the release point so that the coordinates of the brick align with the positive y axis resulting in positive velocity.
• Finally, reference frame is also important. Since we are using the gravitational acceleration as the catalyst to the velocity, we want to keep the reference frame to a laboratory one. This means we should not conduct this experiment on mars or say a moving elevator where acceleration would differ.

In summary, this investigation is science. In this experiment, we used scientific method of measuring and plotting the effects of height on a cart moving down the ramp. With this experiment we attempt to answer what one of the many variable affects the speed of an object. With the data that we have collected we graphed it and noticed the trend line. The higher the height of the ramp, the faster the velocity. We directly made an observation through this experiment to test our understanding of speed and how height can directly cause the speeds to increase or decrease.