Lesson 4— 4.2 Taking accurate measurments

• Natuurkunde / Scheikunde
• Middelbare school
• havo, vwo
• Leerjaar 2

This lesson

• Recap
  
•  Measuring time Precisely
• Reaction time

Learning goals

•  Define reaction time
•  Know how to measures time precisely
•  Measure your own reaction time

What did we cover 

previous lesson?

Formula for speed

Speed=​time​​distance​​

v=​t​​d​​

v: velocity

d: distance

t: time

Rearranging the formula for speed

v=​t​​d​​

3=​2​​6​​

Rearranging the formula for speed

v=​t​​d​​

Speed: 

Distance:

d=v⋅t

Time:

t=​v​​d​​

Converting 

km/h <-> m/s 

4.2 Taking accurate measurements 

Key concepts

•  Precision
• Accuracy
• Significant figures
•  Reaction time
• Timing gates

 Precision and accuracy?

Precision and accuracy

Accuracy: How close the measurement is to the actual value.

Precision: How refined or consistent the measurement is, shown in the number of significant numbers.

Usain bolt

Time:

Yohan Blake

Time:

Justin Gatlin

Time:

2012 olympics — 100 m sprint

Usain bolt

Time: 10 s

Yohan Blake

Time: 10 s

Justin Gatlin

Time: 10 s

Their 2012 times

1 significant number

Usain bolt

Time: 9.6 s

Yohan Blake

Time: 9.8 s

Justin Gatlin

Time: 9.8 s

Their 2012 times

2 significant number

Usain bolt

Time: 9.63 s

Yohan Blake

Time: 9.75 s

Justin Gatlin

Time: 9.79 s

Their 2012 times

3 significant number

All zeros between nonzero numbers are significant numbers 

5006        4 significant numbers

407            3 significant numbers 

Zeros to the right of non zero numbers are insignificant

500   one  significant number

8000 one significant number 

Precision and accuracy

Accuracy: How close the measurement is to the actual value.

Precision: How refined or consistent the measurement is, shown in the number of significant numbers.

Significant figures: The number of digits in a measurment that are meaningful for the measurement.

Key concepts

•  Precision
• Accuracy
• Significant figures 
•  Reaction time
• Timing gates

Reaction time?

Timing gates?

Precision and accuracy

Accuracy: How close the measurement is to the actual value.

Precision: How refined or consistent the measurement is, shown in the number of significant numbers.

Significant figures: The amount of digits in a measurment that are meaningful for the measurement.

Reaction time: The time it takes for you to react to something.

Timing gates: Two camera’s a certain distance apart from each other which record if an object passes it.

Worksheet

Homework

for next lesson

• Do the workbook exercises §4.2
•  Complete the worksheet

Learning goals

•  Define reaction time
•  Know how to measures time precisely
•  Measure your own reaction time