PHY 201 L Name: Sample Final Exam The final exam consists of multiple choice que

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PHY 201 L Name: Sample Final Exam The final exam consists of multiple choice questions, short answer questions, and lab practical questions. Below you will find examples of the type of questions asked. You will have 20 minutes to Complete each of the practical questions. You may only bring a pencil and calculator to the exam and you will work alone 1.) A student makes five measurements of their reaction time. The measurements are 222ms, 235ms, 237ms, 239ms, and 242ms. What should be the reported value for the reaction time? 2.) A rectangle has sides measured to be 4.0 t 0.2 cm and 3.0 0.1 cm. What is the area of the rectangle, including its uncertainty? 3.) To the right is a linear plot of the velocity squared versus the position for an object. If the velocity is measured in cm/s and the position is measured in cm, what are the units of the slope of this graph? position (cm) 4.) The period of a mass on a spring is given by: T 2 m/k) 1/2 two springs Consider with different spring constants. When identical masses are attached to the two springs will the stronger spring with the larger spring constant have a period that is larger or smaller than the period for the weaker spring with a smaller spring constant? 5.) When two objects in a perfectly isolated system undergo a collision, is total momentum always conserved? Is total kinetic energy always conserved? 6.) Starting from rest, a cart moves down an inclined air track. Assume the air track is frictionless. As the cart moves down the air track, does the cart's speed increase decrease, or stay the same Does the cart's acceleration increase, decrease, or stay the same? A compound pulley is a device with multiple pulleys attached to it. How is the tension in the string holding up the compound pulley affected by using different numbers of pulleys on the compound pulley?

Explanation / Answer

1) five measures taken by the student are 222 ms, 235 ms, 237 ms, 239 ms, 242 ms

reported value of the reaction time should be the average of the recorded times

average value = total of reaction time / number of times measure taken

average value = (222 + 235 + 237 + 239 + 242) / 5

average value = 235 ms

reported value of the reaction time = 235 ms

2) the sides of the rectangle is measured to be 4.0 +/- 0.2 cm and 3.0 +/- 0.1 cm

percent uncertainity in the length = (uncertain length / length) * 100

percent uncertainity in the length = (0.2 / 4) * 100

percent uncertainity in the length = 5 %

percent uncertainity in the width = (uncertain width / width) * 100

percent uncertainity in the width = (0.1 / 3) * 100

percent uncertainity in the width = 3.33 %

Area of rectangle = length * width

Area of rectangle = 4 * 3

Area of rectangle = 12 cm^2

The rules for propagation of error state that when two quantities are multiplied, their fractional uncertainties are added

percentage uncertainity in area = 5 % + 3.33 %

percentage uncertainity in area = 8.33 %

so,

uncertainity in area = 12 * 8.33 / 100

uncertainity in area = 0.9998

area of rectangle = 12 +/- 0.9998 cm^2

3) slope of the graph = change in y axis / change in the x axis

unit of slope = (cm^2 / s^2) / cm

unit of slope = cm / s^2

4) according to the formula time period is inversely proportional to the spring constant

so,

more the spring constant less the time period and vice versa

so the stronger spring with larger spring constant have a period that is smaler than the period for the weaker spring

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