The driver's foot pushes the master piston of a car's brakes, of area 2.5 cm², with 180 N.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The driver's foot pushes the master piston of a car's brakes, of area , with . The brake liquid carries the pressure to each wheel's piston, of area . Find the pressure in the liquid and the force on each wheel's piston.
Need a reminder? The key ideaShow
Pressure is force per unit area, , in pascal. Below the surface of a liquid, ; the gauge pressure is . Pascal's law: a change of pressure in an enclosed fluid reaches every part of it, so a hydraulic machine gives .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Pressure. .
Step 2. Each wheel. .
Answer: ; at each wheel.
Check. The area ratio is , and .
Watch out. Every wheel gets the full pressure; the force is not shared out.
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