unit 3 force and pressure

Question 1

contact force

Answer 1

frictional force - opposes or tends to oppose motion between surfaces in contact
air resistance - a type of frictional force exerted by air to oppose the motion of moving objects
normal force - a push exerted by a surface on an object pressing on it
tension - a pull exerted by a stretched spring ,string or rope on an object attached to it

Question 2

non contact force

Answer 2

gravitational force - a pull acting on an object due to earth’s gravity
magnetic force - attractive or repulsive force between magnets
electrostatic force - attractive or repulsive force between electric charge

Question 3

mass

Answer 3

mass is the measure of the amount of a matter in an object
SI unit ( kilogram kg )
beam balance or electronic balance are used to measure
the mass of an object is constant , it is not affected by the gravitational field strength of a planet

Question 4

weight

Answer 4

the gravitational force acting on an object that has mass
formula : w = mg
SI unit ( newton n )
can be measured using a spring balance

Question 5

gravitational field

Answer 5

all objects with mass attract each other . this attractive force between objects with mass is known as the gravitational force or force due to gravity or weight
a gravitational field is a region in which a mass experience a force due to gravitational attraction

Question 6

gravitational field strength

Answer 6

the gravitational field at a point describes how strong or weak a gravitational field is at that point
unit : N/Kg
the gravitational field strength near the Earth’s surface is about 10 N/Kg

Question 7

resultant force

Answer 7

F = ma
this shows that gravitational field strength and acceleration due to gravity are equivalent quantities

Question 8

density

Answer 8

the measure of mass per unit volume
SI unit (Kg/m^3)
an object floats on a liquid if its density is lower than the liquid
an object sink on a liquid if its density is higher than the liquid
formula : p = m/v

Question 9

pressure

Answer 9

a force acting perpendicularly on unit area of a surface
formula: p = F/A
SI unit ( pascal ,Pa)
factors affecting the magnitude of pressure:
1) force acting perpendicularly on a surface
2)area of contact