application of forces

• a force is a push or pull
• the SI unit for force is newtons (N)
• a force can cause a stationary object to move
• a force can cause a moving object to become stationary
• a force can change the speed of a moving object
• a force can change the direction of a moving object
• a force can change the size and/or shape of an object
• a force can exert pressure on an object
• a force can cause turning effects in an object
• contact forces exist between objects that are in direct contact
• non-contact forces do not require objects to be in direct contact
• frictional force is the force that opposes motion between surface with contact
• the direction of friction is always parallel to the surface of contact and opposite to the direction of motion
• friction can slow down a moving object
• friction can prevent a stationary object from moving
• air resistance tends to slow down an objects motion
• elastic spring force is the force acting on a stretched or compressed elastic object to return to its original shape
• tensional force is a pulling force exerted by a stretched spring, cable, string or rope on an object that is attached to it
• normal reaction force is the pushing force exerted by a surface on an object pressing on it
• the normal reaction force is always perpendicular to the surface of contact
• gravitational force is the force that exist between two masses
• weight acts in the downward direction, towards the center of the earth
• the formula for W (weight) is W=mg
• W=mg - W is weight (in N)
• W=mg - m is the mass of the object (in kg)
• W=mg - g is the gravitational field strength (in N/kg)
• gravitational field strength is the gravitational force acting per unit mass
• magnetic force is the force exerted by a magnet on another magnet or a magnetic material
• unlike poles attract
• like poles repel
• electric (electrostatic) force is the force that exist between electric charges
• like charges repel
• unlike charges attract
• balanced forces are when forces acting on a object cancel out each other completely, thus the resultant force is 0
• unbalanced forces are when forces acting on an object do not cancel each other out completely
• pressure is the force acting per unit area
• the formula for pressure is P= F/A
• the greater the force applied, the greater the pressure
• the greater the surface area, the smaller the pressure