Chapter 1: Force and Pressure
what is force
when we push or pull an object, we exert a force
effects of force
change the direction of moving objects
change the speed of moving objects
change the state of rest or motion of a body
cause objects to turn
change the size and shape of objects
types of forces
contact forces
non-contact forces
frictional force
magnetic force
gravitational force
frictional force acts when 2 surfaces are in contact with each other
force of attraction or repulsion between two magnets
force of attraction between two bodies
friction acts in the opposite direction to motion
how to reduce friction
apply lubricants like grease or oil to the surfaces in contact
preventing or reducing contact between the two objects
attach ball bearings to the surfaces in contact
having a smooth body reduces water and air resistance
having a streamlined body shape
can act at a distance
Weight of a body is the gravitational force acting on it
weight
mass
amount of matter in a body
gravitational force acting on a body
SI unit: kilogram(kg)
SI unit: newton(N)
formula
W=mxg
pressure
force acting per unit area
formula
P=F/A
the smaller the area, the greater the pressure. the greater the area, the smaller the pressure
SI unit: pascal(Pa)
knife's cutting edge is very thin, allowing the knife to cut objects easily
caterpillar tracks on tanks increase the area of the tank touching the ground, reducing pressure on the ground and allowing the tank not to get stuck in mud