20. Speed and Density

Note:

Use Q1 and Q5 from Speed, Distance and Time and Q3 and Q4 from density, mass and volume.

Speed and Density FSQ2

In 2009, Usain Bolt set the Men’s $100$m sprint world record in $9.58$ seconds.

Speed and Density FS2(a)

Calculate his speed over this distance in m/s, assuming it is constant.

Give your answer to two decimal places.

Answer type: simple

Answer: 10.44 (m/s)

Workings:

Speed = distance $\div$ time, so

Speed $= 100 \div 9.58= 10.44$ m/s ($1$ d.p.)

2 marks

Speed and Density FS2(b)

Using your rounded answer from part (a), estimate how far Usain Bolt would be able to run in $2$ minutes, assuming he was able to maintain this speed.

Give your answer to $1$ decimal place.

Answer: 1252.8 (m)

Workings:

$2$ minutes is equal to $120$ seconds

The distance is equal to speed $\times$ time, so

Distance $= 10.44\times 120 = 1252.8$ m

2 marks

Speed and Density FSQ6

Molly wants to measure the density of a block of ice.

She measures the mass of the block to be $10.2$ g

She then measures the volume by placing the ice into a beaker of water and measuring the change in volume, as shown in the diagram below:

The initial water level in the beaker was $25.0$ cm$^3$

The water level after the ice was added was $36.1$ cm$^3$

Calculate the density of the ice in g/cm$^3$

Give your answer to two decimal places.

Answer type: simple

Answer: 0.92 (g/cm$^3$)

Workings:

The volume of ice is equal to $36.1-25.0 = 11.1$ cm$^3$

The density is given by the mass $\div$ volume:

Density $= 10.2 \div 11.1 = 0.92$

3 marks