Physics Motion Quiz 02

The approximate mass of a high school student (in kilograms) is:

• 1

• 5

• 65

• 250

Answer explanation

The approximate mass of a high school student is around 65 kilograms, which is a typical weight for teenagers. The other options, 1, 5, and 250 kilograms, are unrealistic for this age group.

The approximate length of a baseball bat is:

• 1 mm

• 1 cm

• 1 m

• 1 km

Answer explanation

A baseball bat typically measures around 1 meter in length, making 1 m the correct choice. The other options, 1 mm, 1 cm, and 1 km, are either too short or too long for a standard baseball bat.

A friend claims that he can measure exactly how much water is in a one-gallon jug after taking a drink from it. You disagree with your friend. Which of the following reason would a scientist give for agreeing with you?

• All measurements contain random errors.

• A perfect measurement requires scientific expertise, which your friend does not have.

• A perfect measurement requires a very expensive instrument, which your friend cannot afford.

Answer explanation

A scientist would agree with you because all measurements inherently contain random errors, making it impossible to measure the exact amount of water after taking a drink.

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:

• a random error.

• an operator error.

• a systematic error.

• a predictable error.

Answer explanation

The different measurements from the three students indicate variability due to random factors, such as slight differences in technique or environmental conditions. This is an example of a random error.

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.

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

• average all the values of each group.

Answer explanation

Averaging all the values from each group takes into account all measurements, reducing the impact of outliers and providing a more accurate estimate of the soccer field's length compared to other methods.

A friend measures the length of the school soccer field to be sure that it is the correct size. Which measuring device will most likely help your friend get the most accurate answer?

• A meter stick accurate to the nearest mm.

• A 30-cm ruler accurate to the nearest mm.

• A 50-m tape measure accurate to the nearest cm.

• A meter stick accurate to the nearest cm.

Answer explanation

The 50-m tape measure is the best choice as it can measure the entire length of the soccer field accurately to the nearest cm, making it suitable for larger distances compared to the other options.

What is the best measuring tool for measuring the length of a hallway and why?

• A meter stick because it is more accurate.

• A tape measure because you can take fewer measurements.

• A tape measure because it uses standard American units.

• A meter stick because it uses SI units.

Answer explanation

A tape measure is the best tool for measuring a hallway because it allows for continuous measurement without needing to reposition frequently, making it more efficient and practical for longer distances.

You are driving on a highway that that posts a 65 mph speed limit. Your speedometer is accurate within 5 mph. What is the maximum reading your speedometer can give that you will be sure is not over the speed limit? (Give the number without units.)

Answer explanation

To ensure you are not over the 65 mph limit, account for the 5 mph inaccuracy. The maximum safe speed is 65 - 5 = 60 mph. Therefore, the highest speedometer reading that guarantees compliance is 60.

Tags

NGSS.MS-PS2-2

What is the difference between accuracy and precision?

• They mean pretty much the same thing.

• Accuracy is being close to a known value; precision is having multiple results that are similar.

• Accuracy is getting the same result over and over; precision is being right.

• Accuracy is having multiple results that are similar; precision is being close to a known value.

Answer explanation

The correct choice explains that accuracy refers to how close a measurement is to a known value, while precision indicates the consistency of multiple measurements. This distinction is crucial in understanding measurement quality.

A:  Two students measure the same length and obtain values of 3 meters and 10 meters.

B:  Two students measure the same length and obtain values of 3 meters and 3.01 meters.

Why are there differences in the measured values?

• In A there is a systematic error; in B there is a random error.

• In A there is a random error; in B there is a systematic error.

• In A there is a random error; in B there is an operator error.

• In A there is an operator error; in B there is a systematic error.

• In A there is an operator error; in B there is a random error.

Answer explanation

In A, the large discrepancy (3m vs 10m) suggests an operator error, likely due to misreading or miscalibrating the measurement tool. In B, the small difference (3m vs 3.01m) indicates a random error, which is typical in precise measurements.