Chapter 1: Review Game (Driving the Roads)

A student is testing her reaction time by trying to keep a light bulb on for exactly 4s by matching a stopwatch. When she turns the light bulb off, the stopwatch reads 4.13 s. What is her reaction time?

• 3.87 seconds

• 0.26 seconds

• 0.13 seconds

• 4.00 seconds

Answer explanation

0.13 s. The student’s reaction time is the difference between when the stopwatch

hits 4 s and the time it takes for her to respond by stopping the stopwatch. If she

would have stopped the stopwatch in exactly 4 s, the answer would have been

1.a). The other answers are not related to the reaction time.

Which of the following will have no effect on the reaction time of a person driving an automobile?

• The age of the driver

• Distractions in the environment

• The speed of the automobile

• Talking on a cell phone while driving

Answer explanation

All the other answers are distractions, which will slow down a driver’s reaction

time. The automobile’s speed does not affect how quickly a person can react, but

will affect how far the automobile travels before the reaction starts to take effect.

A race car driver is being tested for reaction time. In several practice trials, the driver’s

reaction time was recorded as 0.18 s, 0.22 s and 0.17 s. What was the driver’s average reaction time?

• 0.57s

• 0.17s

• 0.19s

• 0.22s

Answer explanation

The average reaction time is calculated by adding the three reaction times and

then dividing by three. The highest or lowest values are reaction times for one

trial only, and may be either too high or too low for various reasons.

A student drops a ruler to test her reaction time, and catches it at the 19-cm mark.

According to the graph below, her reaction time is closest to

• 0.1 s

• 100s

• 0.2s

• 0.25s

Answer explanation

According to the chart, the ruler will fall a distance of 19 cm in a time of almost

0.2 s. This is not because 0.19 is closest to 0.2!

Two students are having a contest to see who has the quickest reaction time. A third

student gives them both stopwatches that were started at the same time and tells them to

stop them when he says stop. The student with the quickest reaction time will have the

stopwatch with the

• broken timer

• time nearest the school clock

• highest time recorded

• lowest time recorded

Answer explanation

The student who reacts in the least amount of time after the stopwatches are

started has reacted the quickest.

The approximate mass of a high school student is

• 1.0 kg

• 5.0 kg

• 65 kg

• 250 kg

Answer explanation

A high school student might have a weight of 140 lbs. At 2.2 lbs/kg, this is

approximately 65 kg. A mass of 5 kg would be 12 lbs. A mass of 250 kg would

be 550 lbs.

The approximate length of a baseball bat is...

• 1 cm

• 1 km

• 1 meter

• 1 millimeter

Answer explanation

A baseball bat is approximately 36 in. long, and a meter stick is about

39 in. long. A length of 1 cm is about 1

2 in., a millimeter is even smaller, and a

kilometer is about 3000 ft long.

Three students measure the length of their classroom and get the following values:

Student A – 6.54 m

Student B – 6.57 m

Student C – 6.52 m

Because all three students received three different measurements, this is an example of

• an uncertainty error

• a predictable error

• a random error

• a systematic error

Answer explanation

Measurements that vary around the correct value would be an example of

random error.

If all the measurements were on the same side of the accepted

value (either higher or lower), the error might be systematic.

The other answers are made-up terms.

Students in a class measure their stride, and use that measurement to determine the length

of a school’s soccer field. As a result, each group arrives at a different value for the length of

the field.

The way to achieve the most accurate value for the length of the field would be to

• get the class to agree on using one group’s value.

• pick the highest and the lowest values and average them.

• average all the values of each group.

• have everyone measure again, and then find out which number is repeated.

Answer explanation

Agreeing on one group’s value does not improve the accuracy, although choosing

the highest and lowest values may work. If most of the values were high and

one value was much lower, it would most likely lead to a false result. Having

a repeating value does not mean that this is anywhere near the correct value,

because it may be due to a systematic error.

An automobile travels between the 100-m and 250-m markers on a highway in 10 s.

The average speed of the automobile during this interval is

• 10 m/s

• 15 m/s

• 25 m/s

• 40 m/s

Answer explanation

The average speed is the distance traveled/time needed to go that distance. The

distance between the markers was 150 m (250 m2100 m), so the speed was

150 m/10 s or 15 m/s. Choices 1.a) and 1.c) are wrong because they just use a

distance, not the distance traveled, and 1.d) is wrong because the distances there

were added and then divided by the time, rather than subtracted.