Question

1. You measure the length of a board with a ruler that is older and has a worn-down end. If you align the end of the board with the end of the ruler, what type of uncertainty does the end of the ruler contribute to the measurement?

	A) Random
	B) Systematic

2. The average height of children in kindergarten in Winnipeg is found by measuring the height of one randomly-selected child in every kindergarten class in the city. What type of uncertainty is due to the selection of the sample of children to measure?

	A) Random
	B) Systematic

3. The acceleration due to gravity is calculated by measuring the time for an empty box to fall 10.0 m, starting from rest. What is the type of uncertainty that is contributed by air resistance?

A) Random

B) 5. Systematic 4. find the sample standard deviation of the following set of four values (your answer should have two digits after the decimal place): 1.8 1.2 1.0 2.2 Two forces point in opposite directions. Their magnitudes are F1 and F2 and their uncertainties are ΔF1 and ΔF2. To find the net force, a student must subtract the force magnitudes: Fnet = F1 – F a) Using the addition and subtraction rule for propagation of uncertainties, select the expression for the uncertainty in the net force. Form: r = x ± y Rule: Δr = Δx + Δy A) ΔFnet = ΔF1 - ΔF2 B) ΔFnet = ΔF1 + ΔF2 C) ΔFnet = Δx + Δy D) ΔFnet = 3 b) If the results of the force measurements are F1 = (10.7 ± 0.9) N and F2 = (16.9 ± 0.6) N, what is the uncertainty in the net force (in N) (don't round)? Your Answer: 6. a) The mass of an object is measured to be 127 g with an uncertainty of 12 g. The correctly rounded off uncertainty is g and the correctly rounded off value is g. b) The force on an object is measured to be 0.423 N with an uncertainty of 0.67 N. The correctly rounded off uncertainty is N and the correctly rounded off value is N. 7. Two friends borrow police radar guns to record the speeds of cars driving through the stop sign outside their elementary school. They both observe one car that is driven particularly recklessly. The first person measures the speed to be 30.65 m/s with an uncertainty of 0.27 m/s while the second one measures the speed to be 30.01 m/s with an uncertainty of 0.36 m/s. The two measurements agree within their uncertainties. Question 1 options: A) True B) Fals

Answer 1

1.

In this case we have a systematic error because the rule is worn and produces incorrect results. This result can be corrected.
Answer: Systematic error.

2.

In this case we have a random error because the child's height cannot represent the average height, this value cannot be estimated.

Answer: Radom error

3.

The contribution of air resistance cannot be estimated. We have a random error.

Answer: Random error