Physics lab report

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Lab Exercise 2: Acceleration

  • Follow the instructions and directions below for this lab.  Disregard the outline in the manual for your LabPaq Kit.
  • Read this document entirely before starting your work.
  • Do not forget to record your measurements and partial results.
  • Submit a Laboratory Report through Moodle, as shown in the last section of this outline.  Remember that the Laboratory Report should include the answers to the questions below.


To calculate the acceleration of an object rolling down an inclined plane.


Acceleration is the change in the velocity of an object. Velocity is a vector quantity with both direction and magnitude. Acceleration is also a vector quantity with both direction and magnitude. If the speed of an object is changed, that object has accelerated either positively or negatively depending on whether it increased or decreased in speed. Another way to accelerate an object is to change its direction of movement. This means that a car going around a corner is undergoing acceleration because its velocity in terms of direction is changing even if the car’s speed, as seen on the speedometer, is constant.


As discussed above, an object falling under the influence of gravity accelerates. From your studies, you can recall the key kinematic equations for the uniformly accelerated motion of an object starting from rest, where v = velocity, a = acceleration, and d = distance.

Using these equations it is then possible to solve for the unknown variables.


In this lab experiment, we will measure the time it takes for a marble to roll down an inclined plane.  From the experimental data, we will then estimate the value of gravity (g).



Set up a ramp as shown in Figure 1 that will be our inclined plane.  Depending on the distance of your ramp, mark intervals of 40 to 60 cm.  For example, in Figure 1, the marks are at 50 cm.  Ideally, the marks should be as separated as possible in order to obtain a better reading.  The height of the ramp is also going to play a role in the accuracy of your measurements. The steeper the slope is, the ball will run down faster and will make measurements less accurate.  Before starting with the measurements, you may want to run some trials in different conditions.


Figure 2: Experimental setup


Figure 2 shows the setup used by a student who did this lab some time ago. In this case, the marks are spaced 40 cm. This experiment works best with gentle angles of elevation. You may get better result if you use a smaller slope than Figure 2 shows. The recommended angles should be around 5 degrees, 10 degrees, and  15 degrees.You also need to record the angle of the inclined plane making a plumb line with the protractor as shown in Figure 3. The angle of elevation from this protractor is around 120.


Figure 3: Measuring the angle of an inclined plane


Measuring Time

Our procedure will consist of dropping the marble at the top of the inclined plane and measuring  with the stopwatch the time it takes to reach each one of the markings, starting with the closest to the point where you release the marble.  Using the example shown in Figure 1, we will first measure the time it takes for the ball to go from 0 cm to 50 cm.  As we learned in Laboratory Experiment #1, it is always good practice to repeat the measurements several times  (in our case 5 times) to reduce errors.

When we have taken and recorded the 5 trials for this first measurement, we will proceed by repeating the experiment but in this case measuring the time that it takes for the ball to reach the second mark  (in the example of Figure 1, it will be from 0 to 100 cm).


Equations used for this experiment

The known variable in this experiment is the distance between the marks.  The measured variable in this experiment is the time it takes for the ball to travel a specified distance.


For a body undergoing accelerated movement, the equations that we will use are:




What is the distance between two marks in your inclined plane?



What is the angle of your inclined plane with respect the horizontal?  (0° would mean the inclined plane totally horizontal, so the ball would not move;  90° would mean the board totally vertical)


Write down these two values in the table we will use to record all our measurements. It will also be used at the end of the lab.

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