Physics Lab Report
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Laycee Clark October 30, 2015Period 7 A force is any push or pull on an object that may result in a change in an object’s motion. Acceleration is speeding up, slowing down, or changing direction. To determine acceleration from a graph, it needs to be a velocity graph in which the x-axis is labeled with a unit of time, usually seconds, and the y-axis is labeled with velocity, in meters/second. When you slope a velocity graph (taking velocity of meters/second and dividing it by the time in seconds), you will end up with a number and a unit of meters/second/second. This unit is the unit for acceleration. Below is an example of a graph that was recorded during lab, with velocity on the y-axis and time on the x-axis.[pic 1] This lab was completed with a procedure that did not have many steps. First, a string was attached to a gray plate on the back of a small cart. At the end of the string was a cup. The string was then placed on a wheel that acted like a pulley system (see figure 1). So, as the cart moved toward the end of the table, the cup moved lower toward the ground. A stack of books was placed on the ground underneath the cup. The cart started near the opposite end of the table, and as it was let go, time was recorded to see how long it took for the cup to hit the books on the ground. Pennies were added to the cup to see if the mass changed how fast the cup hit the books.
The way acceleration was found was through a motion sensor system (the green boxes on the counter in figure 1) on the computer. As the cart was let go, the motion sensor picked up on its motion and made two graphs, one a regular speed graph that gave meters/second when sloping it, and a velocity graph that gave acceleration when sloping it. Referring to the example graph above, acceleration of the cart before the pennies hit the books was found by sloping part A of the graph. Find acceleration of the cart after the pennies hit the books was found by sloping part B of the graph. The purpose of the lab was to determine if there was a relationship between forces and velocity or forces and acceleration. The cup of pennies was the force, so when it landed on the books, no more forces were considered to be acting on the cart in the horizontal direction. [pic 2]Figure 2Number of pennies in cupAcceleration before pennies hit the books (m/s2)Acceleration after pennies hit the books (m/s2)70.2015 m/s2-0.00728 m/s2200.4301 m/s2-0.08470 m/s2330.5791 m/s2-0.04554 m/s2