Methodology

Energy can exist in numerous forms such as internal (sensible, latent, chemical and nuclear), kinetic, potential, electric and magnetic, and their sum constitutes the total energy, E of a system. However, only the kinetic energy, KE and potential energy, PE as well as the internal energy, U are taken and majorly considered in this experiment. Because in the absence of electric, magnetic and surface tension effects, the change in the total energy of a system during a process is the sum of the changes in its internal, kinetic and potential energies and can be expressed as below: ∆E = ∆U + ∆KE + ∆PE (2.2) This experiment is proposed to find the effect of different slopes on the speed of a cart. Therefore, there are some apparatus that will be used to conduct this experiment. First of all, a cart of 1 kg of mass is selected to be the system. Then a linear glass track, a stopwatch, a few blocks, and a measuring tape are prepared before starting the experiment. Consider a cart that is placed on a glass track that is raised at one end to form an inclined plane whose angle of inclination is ϴ. The cart moves down the inclined plane with a speed, v. Figure 2.1 shows a cart on a glass track that represents the experiment that will be conducted later on.

Figure 2.1: An experiment to find the effect of different slopes on the speed of a cart. This experiment is carried out on the linear floor. To begin, two blocks of approximately 10 cm in height for each are placed under the support at one end of the glass track. The height, h of the two-block is then measured by using a measuring tape and is recorded in the Data Table. The glass track is now raised to form an inclined plane whose angle of inclination is denoted as ϴ as shown in the figure 2.1. The distance, d between the points of support of the glass track is measured and recorded (figure 2.1). The cart is released from rest at the top of the inclined and simultaneously a stopwatch is started. A person is needed to release the cart and another to start the stopwatch. The stopwatch is then stopped once the cart reaches at the bottom of the track or when it hits the ground (the linear floor). The time is recorded in the Data Table. The above steps are repeated for the different heights; that is by changing the two blocks to four blocks, six blocks, eight blocks, and ten blocks. All the times taken from each different height are again recorded in the Data Table. In this experiment, the block is used to raise the glass track so that it will form an inclined plane. As by adding up the blocks, there are changes in the slopes. That is the amount of angle, ϴ will also change. The glass track is used

to make a smooth surface, in order to assume that there is zero or no frictional force acting upon the system. It is only the speed that is needed to be taken into account regardless of the frictional force that acting on the cart; that is this experiment is frictional-force free. For the calculation, the value of sin ϴ = h / d and it is recorded in the calculations Table. By taking the values from the Data Table, a few graphs are constructed. The Data Table and the calculations will be discussed in the next part that is the discussion.

2.0 METHODOLOGY The experiment that will be carried out is to prove the first law of thermodynamics. In the experiment, the height of the plane above the horizontal acts as the variable. By changing the height (adding up the numbers of block which is used to control the height), there will result in change to the slope and as well as there will be a different amount of angle of the plane above the horizontal. Thus, this will affect the velocity or speed of the cart that is used as a system in this experiment. As it was discussed in the introduction part, the first law of thermodynamics is simply an expression of the conservation of energy principle. It asserts that energy cannot be created nor destroyed; it can only change from one form to another but the total amount of energy remains constant. Noting that energy can be transferred in the forms of heat, work and mass, and that the net transfer of a quantity (increasing or decreasing in the total energy of the system during a process) is equal to the difference between the amounts transferred in and out during a process. The energy balance thus can be expressed as: ∆Esystem

Ein ─ Eout = (Qin ─ Qout) + (Win ─ Wout) + (Emass,in ─ Emass,out) = (2.1)

In thermodynamics, it only deals with the change of the total energy, E of system because thermodynamics provides no information about absolute value of the total energy. Thus, the total energy of a system can be assigned a value of zero (E=0) at some convenient reference point.