# Y9 forces

 What is a moment? The turning effect of a force How are moments calculated? Moment (Nm) = Force (N) x distance from pivot (m) What is a pivot? The point around which something turns What is fulcrum an alternative word for? Pivot What is a lever? Something that uses moments to make a task require less force (make it easier) Name some examples of levers Can openerScissors (especially nail scissors)Wheel barrowCrowbarWheel spanner What do we know about the anti-clockwise moment and the clock wise moment if an object is not turning? They are balanced What are the units for force? Newtons (N) What are the units of distance? Metres (m) What are the units of moments? Newton metres (Nm) What is a pendulum? An object that swings to and fro What affects the time that a pendulum takes to make a complete swing? The length of the pendulum (nothing else!) What name we give to the time for a pendulum to make a complete swing (back to its starting place)? Time Period What unit is used to measure time? second (s) What unit is used to measure speed? Metres per second (m/s) What unit is used to measure acceleration? Metres per second squared What is the equation for calculating acceleration? change in speed / time taken Name the force that keeps objects moving in a circle Centripetal force In which direction does centripetal force act? Towards the centre of the circle What is the unit of centripetal force? Newtons (N) What three things affect the size of the centripetal force needed to keep an object moving in a circle? Radius of the circleSpeed of the objectMass of the object Does increased speed need a larger or smaller centripetal force? Larger If the radius of the circle increases, what effect does this have on the centripetal force needed? It reduces If the mass of the object increases, what effect does this have on the centripetal force needed? Increases What provides the centripetal force that keeps the Earth orbiting around the Sun? Gravity What provides the centripetal force that keeps a conker tied to a piece of string moving in a circle The tension in the string In which direction does air resistance act? Opposite to the direction of travel If the speed of an object increases, how does this affect the air resistance? Air resistance increases If forces are balanced what do we know about the speed of an object? It moves at a constant speed.(If it was not moving it stays not moving) What is terminal velocity? The speed an object moves at when the forces acting on it are balanced.eg a skydiver falling when her weight and air resistance are equal Why does opening a parachute increase air resistance? The parachute has a large surface area What are the two units of pressure?  or Pascals (Pa) What is the equation to calculate pressure? What are the units for Area ? What is inertia a measure of? How hard to start or stop something moving What two things affect the inertia of an object? MassSpeed When a skydiver is falling, does her weight or air resistance change as her speed changes? Air resistance (Her weight is constant) AuthorAHutson ID244293 Card SetY9 forces DescriptionY9 forces Updated2013-11-01T10:48:10Z Show Answers