Motion & Force

Motion Main variables in motion : speed(velocity) Travel Time acceleration

Relationship between speed, distance & time V = d/ ∆t V = average speed (in m/s) d= distance travelled (in m) ∆t = time variation (travelling time in s)

Example What is the speed of a car that travels 5 km in 5 minutes? V= d/ ∆T V= 5000 m/ 300 s V= 16.67 m/s

Forces and changes in motion A force is an action that can change the motion of an object, or deform the object, by pushing or pulling on it.

Force is measured in newtons (N) 1 N = 1 Kg x 1 m/s Force is always exerted by one body on another, and in one direction

Types of Forces Gravitational Force Electromagnetic Force Friction Nuclear Forces

Gravitational Force A force of attraction acting between all objects as a result of their masses and the distance between them. Greater the masses = greater the force Greater the distance = weaker the force Gravitational force in Earth = 9.8 N/Kg

The relationship between mass & weight Mass = measures the quantity of matter in an object Weight = measures the gravitational force acting on an object. w = m x g w = weight (N) m = mass (kg) g = gravitational force (N/Kg)

Electromagnetic Force Force of attraction or repulsion between two objects with an electrical charge or with magnetic poles

Friction Friction is a force that prevents two objects from slipping over each other when they come into contact.

Strong and weak nuclear forces Both forces are within the nucleus of an atom. Strong nuclear forces  responsible for the cohesion of atomic nuclei Weak nuclear forces  responsible for radiactivity

Equilibrium of two forces The resultant force is a virtual force whose action is equal to the combination of all forces simultaneously to an object.

P.100 # 13, 15, 16, 17, 18, 19, 20, 21,22,23,24