State the scientific term given to the turning effect of a force.
A heavy security door has stiff, dry hinges that undergo high friction. A security guard opens the door by pushing on its outer edge, which is furthest from the hinges.
To close the door, the guard pushes it in the opposite direction at a point halfway between the hinges and the outer edge.
State two differences between the force required to close the door and the force used to open the door, assuming the same turning effect is required to move the door in both directions.
Suggest one practical method of reducing the force needed to open this door.
245 exam-style questions on CIE IGCSE Physics 1.5 Forces, covering 1.5.1a Forces, resultant force and motion, 1.5.1b Load–extension graphs and the spring constant, 1.5.1c Friction and drag, 1.5.1d Force, mass and acceleration, 1.5.1e Motion in a circular path, 1.5.2a Moment of a force, 1.5.2b Principle of moments and equilibrium, and 1.5.3 Centre of gravity and stability. Each one has a worked solution and a mark scheme showing where the marks go.