PH 2.1 - 2.3

centre of gravity

An imaginary point where you can imagine gravity as being applied to an object.

dynamometer

An instrument with a helical spring that is used to measure forces.

elastic deformation

Deformation in which the object regains its original shape once the force is no longer being exerted.

force

Concept in physics that makes clear how objects change one another’s shape and/or motion.

force scale

Ratio that you use to draw forces. Shows the size of a force that is indicated by an arrow of 1 cm.

gravity

The force with which the Earth attracts you and all the objects around you.

magnetic forces

A force that acts between the two poles of a magnet. It can be an attraction or repulsion.

muscle strength

A force that arises when the muscles in a body contract.

plastic deformation

Deformation in which the object remains deformed after a force has been exerted on it.

resilience

A force that arises when you extend or compress a springy material.

tension

A force that arises in a rope if it is pulled at both ends.

vector

Way of representing the size, direction and point of application of a force as an arrow.

directly proportional

Two variables are directly proportional if they increase or decrease in a fixed ratio: if the one variable increases or decreases n×, the other variable also increases or decreases n×.

extension

The increase in the length of a spring when a force is exerted on it.

normal force

A force that acts perpendicularly to the object’s surface. An example is the force a tabletop exerts on a fruit bowl.

parallelogram method

Method for finding the resultant when two forces have some arbitrary angle between them.

resultant

The sum of the forces acting on an object. The forces have to be added as vectors, not as numbers.

spring constant

Property of a spring that indicates how far the spring extends when a force is exerted on it.

zero position

The length of a spring that has not been extended.

air resistance

Resistance that arises because a moving object has to push the air in front of it aside.

drag coefficient (plus)

A constant that depends on the streamlining of an object.

friction / sliding resistance

Resistance that arises when two surfaces move against one another, such as a ski gliding over snow.

frontal cross-section

The surface of an object or person as seen from in front.

Newton’s First Law

An object for which the resultant is 0 N is either stationary or it moves along a straight line with a constant speed.

resistance

A force that resists a motion and acts against that motion.

rolling resistance

Resistance that arises when a rolling object and the ground both become deformed during the motion.