What does it mean? (Disciplinary Core Ideas) 1. Suppose your friend mistakes a yardstick for a meter stick and measures the length of an intersection in your
neighborhood. Is this error random or systematic? Which of these types of errors affect precision or accuracy?

systematic

Explanation:

Systematic error:

This type of error is the result of an improperly calibrated apparatus or and improperly designed experiment that introduces the same one directional bias into all of the measurements. A systematic error is an effect that changes all measurements by the same amount or by the same percentage. For example, a ruler that has a badly worn one end, will introduce the same amount of uncertainty (in this case systematic errors) is introduced to all measurements. Instrument zeroes should automatically be checked every time an instrument is used.

Random Error:

A random error is a result of fluctuations in experimental conditions (such as repetitive measurements) that cause a measured value to occur above or below the correct value with equal probability. For example, when we read the meter stick with naked eye in successive measurements, we may be unable to judge the position of the markings on the meter stick accurately enough to obtain repeatedly the same result. This results in fluctuations in the measured values. Sometimes, the fluctuations are intrinsic to the system under investigation (as in the radioactive source, where the number of the emerging radioactive particles arises from the basic nature of radioactive decay). These uncertainties (or errors) can be estimated by using statistical methods (average, standard deviation, mean, mode,). Note that there are other uncertainties, such as instrument uncertainty, which can be estimated by personal judgment. For example, the instrument uncertainty of a meter stick is usually 0.1 cm.

what is the speed of a softball that travels 20m in 2secs

speed = 20/2 = 10 m/s

i think it would be 5