Compound Measures Flashcards

All 6 cards in this deck

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

e.g. 180 km/h

1. Multiply by 1000 to change km into m: $180 \times 1000 = 180\,000$ m/h
2. Divide by 3600 to change per hour into per second: $180\,000 \div 3600 = 50$ m/s

How do you convert a density in $\text{g/cm}^3$ into $\text{kg/m}^3$?

e.g. $2.5\ \text{g/cm}^3$

Multiply by 1000: $2.5\ \text{g/cm}^3 = 2500\ \text{kg/m}^3$.

How do you convert a rate of pay in £ per hour into £ per minute?

e.g. £12 per hour

Divide by 60: £12 per hour $=$ £0.20 per minute.

What are the steps to find the mass of a solid from its density?

e.g. a cuboid 2 cm by 3 cm by 4 cm made of metal of density $5\ \text{g/cm}^3$

1. Find the volume: $2 \times 3 \times 4 = 24\ \text{cm}^3$
2. Use mass $=$ density $\times$ volume: $5 \times 24 = 120$ g

What are the steps to find the density of a mixture of two liquids?

e.g. $80\ \text{cm}^3$ of density $1.8\ \text{g/cm}^3$ mixed with $40\ \text{cm}^3$ of density $1.2\ \text{g/cm}^3$

1. Mass of each: $1.8 \times 80 = 144$ g and $1.2 \times 40 = 48$ g
2. Totals: mass $192$ g, volume $120\ \text{cm}^3$
3. Density $= 192 \div 120 = 1.6\ \text{g/cm}^3$

How do you find the time taken to fill a container from its volume and the rate of flow?

e.g. a $3000\ \text{cm}^3$ tank filled at $250\ \text{cm}^3$ per second

Time $=$ volume $\div$ rate of flow: $3000 \div 250 = 12$ seconds.