Flow Rate Worksheet

Flow rate at a glance

Flow rate measures how quickly liquid, such as water flows into or out of a container. The volumetric flow rate is measured in units of volume per time, for example litres per minute ( l/min ), gallons per minute ( gpm ) or millilitres per second ( ml/sec ). 

Flow rate calculations can be done using the formula, text{Flow rate} = text{Volume}divtext{Time} .

We can also calculate the volume or the time taken given the flow rate by substituting in the values we know and rearranging. 

Consider oil passing through a 50cm circular pipe that has a radius of 2cm . The cross-sectional area of the pipe is 4pi cm^2 and the volume when the pipe is full is 200pi cm^3 . If the velocity of the oil through the pipe remains constant (the flow rate), we can determine the amount of oil passing through the pipe.

If the width of the cross-section of the pipe increases (the pipe diameter), more oil can pass through the pipe. The viscosity of a liquid affects the fluid flow rate (water is less viscous than custard and so water flows faster than custard). Hydrostatic pressure also affects flow rate because of the force of gravity.

We calculate flow rates in many real life contexts such as in medicine. The drop factor is the number of drops per millilitre of solution delivered by gravity. If the drip rate changes, the patient could receive too much of too little medicine over the allocated time period, which may affect their health.

Looking forward, students can then progress to additional rate of change worksheets and other ratio and proportion worksheets, for example a ratio worksheet or a simplifying and equivalent ratios worksheet.

For more teaching and learning support on Ratio and Proportion our GCSE maths lessons provide step by step support for all GCSE maths concepts.