2 Force Force- push or pull exerted by one body onto another Not all forces are easily recognizedRight now several forces are acting on all of us.
3 Balanced forcesBalanced forces – equal forces act on an object – and cancel each other outIf the upthrust (or push up) of the air is equal to the force of gravity (pull down), then the balloon remains suspended in the air.
4 Net ForceNet force – when one force is greater then another. This is an unbalanced force- and causes an object to accelerateThere may be many force directions in any one movement
5 NewtonNewton’s first law of motion: An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force
6 ForceForce is equal to the mass of the object times the objects acceleration. If any two of these are known the third can be found.F = m x aMass- kilogramsa = m/s2F = Newtons
7 InertiaInertia = the resistance an object has to a change in its state of motion – objects with greater mass have greater inertia
8 Force is not needed to keep an object in motion. Forces accelerate or decelerate objects
9 FrictionFriction- force that opposes movement between two surfaces that are touchingCauses of friction – unsmooth surface, deformations, molecular attraction
10 QuestionImagine a place in the cosmos far from all gravitational and frictional influences. Suppose that you visit that place (just suppose) and throw a rock. The rock willa. gradually stop.b. continue in motion in the same direction at constant speed.
11 Gravity Gravity is a force that all matter has on all other matter. Gravity is affected by mass and distance-As mass increases gravitation increasesAs distance from the mass increases gravitation decreases
12 ↑ Einstein’s Theory of General Relativity Newton’s Law of Gravitation
13 Gravity MathNear the surface of the Earth gravity accelerates objects at 9.8m/s2Weight is the force of gravity acting on your bodyFind weight (Newtons) by multiplying your mass (kg) by acceleration (9.8m/s2)Your mass is the amount of matter in your body. It does not change based on location.Your weight can change depending on the gravitation of your location. i.e. the moon