KS3 Science · Physics
Pressure, moments and stretching
Eight short lessons. Look at the picture, learn three things, then play.
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Key words
Pressure The force on each unit of area
Area The size of a surface, in m² or cm²
Newton per square metre The unit of pressure (N/m²)
Fluid A liquid or a gas
Upthrust The upward push of a liquid or a gas on an object in it
Atmospheric pressure The push of the air, caused by the weight of the air above
Density How much mass is packed into each cubic centimetre
Extension How much longer a spring gets when it is stretched
Hooke’s law The extension of a spring is proportional to the force on it
Limit of proportionality The point past which a spring no longer follows Hooke’s law
Directly proportional Doubling one quantity doubles the other: the graph is a straight line through the origin
Moment The turning effect of a force
Pivot The point that a lever turns about
Newton metre The unit of a moment (N m)
Lever A rigid bar that turns about a pivot
Work done The energy transferred when a force moves an object
Joule The unit of work and of energy
Machine Something that makes work easier, such as a lever or a ramp