Formula
The formula of density
density equals mass over volume
force that acts on a body because of gravity
weight
Unless a resultant force acts on an object, it will continue to move in a straight line at a constant speed or remain at rest
Newton's first law
Find the potential difference of an electrical appliance given its resistance is 50 Ohms and its current is 8 Amperes.
V = I x R
V = 8 x 50 = 400 V
True or False
When two lamps are connected in parallel circuit, both lamps will not work when one is broken.
False
The formula of work done
Work done equals force times distance
the force between electrically charged objects
electrostatic force
F = m x a
Newton's second law
Find the height of an object given its GPE is 1500 J, the mass of the object is 20 kg and the gravitational force is 10 m/s^2.
GPE = m x g x h
h = 1500 / (20 x 10)
h = 7.5 m
Difference between vector and scalar quantities
Vector quantity takes into account, magnitude and direction,while scalar quantity only takes magnitude.
The formula of finding velocity, given its Kinetic Energy and mass
Square root of (its Kinetic Energy multiplied by two over mass)
Define conduction, convection and radiation
Conduction : transfer of heat through a medium
Convection: transfer of heat through movement difference in density/convection current) of fluid (liquid or gas)
Radiation: transfer of heat without medium
At constant temperature, the volume of a gas is inversely proportional to the pressure
Boyle's Law
In 2 minutes, a particle vibrates 960 times. Find its period and frequency.
Period = T = t/n
= 120/960 = 0.125 s
Frequency = f = n/t
= 960/120 = 8 Hz
how well something converts energy
efficiency
The three formulas used to find the amount of heat needed to turn ice into water vapor
Q = m x c x delta T
Q = m x Lf (latent of fusion)
Q = m x Lv (latent of vaporization)
the rate of transferring energy
Power
increase in length (extension) of a spring is directly proportional to the force pulling on it.
Hooke's law
If the velocity of sound is 340 m/s and the frequency of the wave is 85 Hz, find its wavelength.
wavelength = v/f = 340/85 = 4 m
a commonly wasted energy form
heat/thermal
Beta (area) = 2 x Alpha (linear)
Gamma (volume) = 3 x Alpha (linear)
The mass and velocity of an object
Momentum
Each planet revolves round the Sun in an elliptical orbit with the sun at one focus
Kepler's Law
A convex lens has a focal length of 15 cm. An object is placed 20 cm in front of the lens. Find the distance of the image from the lens.
1/15 = 1/20 + 1/Si
Si = 60 cm
A way to produce electricity from potential energy of water then flowing
Hydro-electric power plants