chp 9 : application of forces and transfer of energy Flashcards
what is forces
a push or pull
what is the SI unit of forces
newton (N)
what do we have to state when describing forces
magnitude and direction (20N downwards)
what are contact forces
frictional force and tension
what are non contact forces
magnetic forces and gravitational force
what are frictional forces
a force that opposes 2 surface in contact
which direction does friction act in
opposite of motion
rollers/ball bearings -> same direction as motion
the ___ the surface, the ___ the heat generated
(frictional force)
the rougher the surface, the greater the heat generated
what does friction depend on
the nature of the surface and the weight of the body , not the size
how can friction be reduced
lubricant, ball bearings and rollers
what is tension
tension resists an elastic object’s change in shape
what direction is tension exerted in
opposite direction of how the object is stretched
what is magnetic force
the force exerted between a magnet and magnetic material
what is gravitational force
an attraction force btwn 2 masses
the ___ the mass, the ___ the force
(gravitational force)
the larger the mass, the larger the force
what is gravitational force also known as
weight
what do we use to measure a pulling force
spring balance
what do we use to measure weight (gravitational force)
spring balance / compression spring balance
what is mass measured with
calibrated electronic balance, beam balance
what is the formula to find gravitational field strength
w=mg
what are the effects of forces
speed, direction, size/shape, pressure
what is moment
a force about a pivot is called the moment of force
____ force, ____ moment
(moment)
larger force, larger moment
____ perpendicular distance, ____ moment
(moment)
larger perpendicular distance, larger moment
what is the formula for pressure
pressure = force/contact
____force, ___ pressure
(pressure)
the larger the force, the larger the pressure
___ contact area, __ pressure
(pressure)
the larger the contact area, the smaller the pressure
SI unit for pressure
Pa
the unit for pressure
N//m2
amount of ___ = amount of ___
(pressure)
amount of force = amt of weight
the water pressure ____ as the depth ___
the water pressure increases as the depth increases
___ altitude, ___ atmospheric pressure
higher altitude, lower atmospheric pressure
describe the atmospheric pressure of drinking straw
as we inhale the water, the air pressure in the straw becomes lower
atmospheric pressure in the cup pushing the water into the straw has a higher air pressure, hence it pushes the water upwards into the straw
what does work done mean
force is applied to the object and the object moves in the same direction as force applied
SI unit of energy
joule (J)
what is energy
the ability to do work
what can energy not do
energy cnt be destroyed or created, it can only be converted
what is potential energy
stored energy
what is chemical potential energy
energy stored in chemical bonds of a substance
what is elastic potential energy
energy stored in an elastic object that is stretched, compressed, deformed
what is gravitational potential energy
energy stored in an object bcos of its position or height above earth’s surface
formula for gravitational potential energy
gpe = mgh
what is kinetic energy
energy an object has bcos of motion
as mass and speed ____, KE ____
as the mass and speed increase, ke increases
formula for ke
1/2mv2
