Forces in One Dimension Vocabulary Section 1 Force

Forces in One Dimension

Vocabulary - Section 1 ▪ Force • Equilibrium ▪ Balanced forces • Newton’s first law ▪ Unbalanced forces • Newton’s second law ▪ Free body diagrams • Newton’s third law ▪ Net force ▪ Contact force ▪ Field force ▪ Inertia • system

Force and motion ▪ In physics, a force is a push or pull ▪ Unbalanced forces change motion ▪ Objects at rest, or not moving, still have forces acting upon them. These are known as balanced forces ▪ Contact forces – forces that directly touch the object (ex. Your hand pushing an object or simply holding an object) ▪ Field forces – forces that are exerted without contact. (ex. Gravity)

Force and Motion ▪ Free body diagrams – a pictorial representation of forces acting on an object – the object is depicted by a dot – Each force is represented by a vector (arrow) showing the direction of the force on the object – The length of the vector must be proportionate to the force acting on the object (use the magnitude of the vector) – Each force must be labeled. Ex. Draw a Free body diagram of a person holding a ball in their hand: Fhand on ball Fgravity

Force and motion ▪ Forces are measured in Newtons ▪ 1 N = kgㆍm/s 2 ▪ The force exerted by an apple on your hand is approximately 1 Newton.

Force and Motion ▪ Net force – the vector sum of the forces acting on an object – To calculate net force: ▪ If forces are being applied in the same direction, then add forces together ▪ If forces are being applied in opposite directions, then subtract forces.

Newton’s 2 nd law ▪

Newton’s 1 st law ▪ Newton’s 1 st law states that an object at rest will stay at rest and an object in motion will continue to move in a straight line with a constant speed if and only if the net force acting on the object is zero. ▪ Newton’s 1 st law is sometimes caused the law of inertia ▪ Inertia – (not a force) - an objects tendency to resist a change in velocity.

Newton’s 1 st law ▪ Equilibrium – the net force acting on an object is zero – An object is in equilibrium if it is moving at a constant velocity. – Being a rest, v= 0, is also equilibrium