General Science Quiz: Simple Machines: Levers, Pulleys and Inclined Planes

Mechanical advantage is defined as the load divided by the effort, so the load is the mechanical advantage multiplied by the effort, that is three multiplied by fifteen, which gives forty-five units.

The velocity ratio is the distance moved by the effort divided by the distance moved by the load, that is ten divided by two point five, which is four.

Velocity ratio is defined as the distance moved by the effort divided by the distance moved by the load in the same interval of time, and because it depends only on the design of the machine it does not change with friction, unlike the mechanical advantage.

A lever is a rigid bar turning about a fulcrum, and by the principle of moments the load multiplied by the load arm equals the effort multiplied by the effort arm, so a long effort arm lets a small effort balance a large load; this is the simplest way of…

In a wheelbarrow the wheel acts as the fulcrum, the load sits in the tray between the wheel and the hands, and the effort is applied at the handles, which is the arrangement of a second class lever; because the effort arm is always longer than the load arm, its…

In a pair of tongs the joint is the fulcrum, the hand presses somewhere in the middle of the arms and the object held lies at the far end, so the effort is between the fulcrum and the load; the effort arm is shorter than the load arm, the mechanical…

In a single fixed pulley the rope that is pulled down moves exactly as far as the load rises, so the distance moved by the effort equals the distance moved by the load and the velocity ratio is one; the pulley gives no gain in force and is used only…

The velocity ratio of an inclined plane is the length of the slope divided by its vertical height, because the load is pushed along the whole slope while it is raised only through the height; here ten divided by two gives five, so in the ideal case an effort of…

The pitch of a screw is the distance between two consecutive threads measured along its axis, and it is also the distance through which the screw advances in one complete turn; the velocity ratio of a screw is the circumference of the circle described by the handle divided by the…

A wedge is two inclined planes joined back to back, and an axe, a knife, a chisel and a nail all work on that principle: a force applied at the blunt end is turned into a much larger sideways force at the sharp edge, and the thinner and longer the…

In every real machine some of the work put in is used in overcoming friction between the moving parts and in lifting the parts of the machine itself, and that work leaves the system as heat and sound, so the work delivered to the load is always less than the…