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Accelerated motion

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The last lab we tried to study an accelerated motion using an inclined plane and a marble. We recorded the time it takes for the marble to cover different distance. We tried to plot distance vs time and we were supposed to find a parabola. (Since d = 0.5 a t² if the initial speed is zero). The lab didn’t work for every one so we are going to try another strategy. We will use a timer tape so you will not have to use a stop watch. The machine makes a mark every 1/60 second.

PURPOSE

Observe and analyze the uniformly accelerated motion We will record the distance d and the time t a cart takes to move along a straight line. The cart starts at rest (V1=0) and  is accelerating. We will use the equations:

a = (V2 - V1 )/t  = V2/t    V2 is the final speed , V1=0 and t is the time

We also know: Vav = (V1 + V2) /2  =  V2/2    Vav is the average speed with V1 = 0

Using Algebra and the equations we can show: a = 2Vav /t

You will record the distance covered by the cart and the time elapsed.

Using the above formula, you will compute the acceleration. (constant)

If you plot distance vs time, you should get a parabola (d = 0,5 a t²  with Vi =0)

 

PROCEDURE

1) Set up the apparatus. Put 500g inside the cart and attach 20g at one end of the string. The other end is attached to the cart,

 

 

 

 

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2) While one student holds the cart still, another student will attach the 20g mass to the loose end of the string that is hanging over the table.

3) While still preventing from moving, turn on the recording timer. Now release the cart, allowing the 20g to pull the cart across the table.

4) catch the cart at the edge of the table to prevent it from knocking loose the pulley or plunging to the floor.

5) Turn off the timer and inspect the timer tape. A dark spot should be visible at the beginning of the tape followed by a series of recognizable dots to analyze.

6) Label the first distinguishable dot “0”. Count off five dots (spaces) from 0 and mark this dot “1” Continue counting off five dots from each previous numbered one and marking them “2”, “3”,”4’…

7) Carefully measure the distance traveled during each interval of time. (for 5 spaces) Record that distance in table 1. Calculate the total distance of the cart at each interval by summing the current distance plus the distance during the preceding intervals. Record the total distance in table1.

 

8) Find the average speed for the whole motion

Vav = total distance / total time

 

9) Estimate the acceleration (see formula above) using the average speed.

 

 

10) Make a graph distance vs time. You can use the TI or excel.

 Y = distance and X = time. The graph is a _____________

That means that Y (distance) caries are the __________ of X (time).

Is it surprising ?

 

11) repeat all the steps with a mass of 30 g. compare the graphs.