Conversions & Standard Form Flashcards

All 6 cards in this deck

What are the steps to convert a quantity with a prefix into its base SI unit?

e.g. 4.5 kJ into J

1. Replace the prefix with its power of ten: k $= \times 10^{3}$

2. Multiply: $4.5 \times 10^{3} = 4500$

3. Answer: 4500 J

What are the steps to convert a time in hours into seconds?

e.g. 2 hours

1. Hours to minutes, $\times 60$: $2 \times 60 = 120$ min

2. Minutes to seconds, $\times 60$: $120 \times 60 = 7200$

3. Answer: 7200 s

What are the steps to convert a speed in km/h into m/s?

e.g. 72 km/h

1. Kilometres to metres, $\times 1000$: 72 000 m each hour

2. Hours to seconds, $\div 3600$: $72\,000 \div 3600 = 20$

3. Answer: 20 m/s

What are the steps to multiply two numbers in standard form and give the answer in standard form?

e.g. $(2 \times 10^{5}) \times (4 \times 10^{3})$

1. Multiply the front numbers: $2 \times 4 = 8$

2. Add the powers of ten: $5 + 3 = 8$

3. Answer: $8 \times 10^{8}$

To how many significant figures should the mean of repeat readings such as 0.74 s, 0.69 s and 0.81 s be given?

The same number of significant figures as the readings — 2 s.f., so 0.75 s.

True or false? A number written in standard form with a negative power of ten, such as $5 \times 10^{-3}$, is a negative number.

False. A negative power of ten means a small positive number (less than 1); $5 \times 10^{-3} = 0.005$.