FORCE, MOTION, AND GRAVITATION Flashcards
what is mass
measure of the
- amount of matter in the object
- a numerical measure of its inertia
what is the symbol for mass
m
what is the measure for m
kilograms (kg)
does mass change
the same on earth and in space
what is weight
the force of gravity on the object
how is weight calculated
(w = mg) weight = mass x acceleration of gravity
what is the unit for weight
Newton (N)
what is the gravity at the surface of the earth
9.8m/s2
What is the force acting on an object in free fall (within earth)?
Gravity
Where does the expression of weight for an object in free fall come from?
From Newton’s second law
What is the centre of mass
point where all of the mass of an object is concentrated.
What happens to an object supported at the centre of its mass?
it will remain in static equilibrium
What is Newton’s first law termed as
Law of inertia
What does Newton’s first law/law of inertia state
Object in a state of motion or a state of rest will remain in that state unless a net force acts upon it.
By what law do passengers inside a bus fall backwards when a bus moves from standstill
Due to inertia of rest
Why do passengers actually fall backwards when a bus moves
Lower part of passenger body moves along with bus.
Upper part of the body retain state of rest (inertia).
Consequently, the passenger will fall backward.
What is Newton’s second law
When object acted upon by net force MEANS
object’s state of motion =
•inversely proportional to the mass (m) of the object.
•directly proportional to the net force (F) acting upon the object.
What is the formula for Newton’s second law
Force = Mass x Acceleration
What is Newton’s third law
For every action, there is an equal and opposite reaction
Contextualise Newton’s third law to an example of object A and object B
This means that when object A applies a force to object B, object A will experience a force of equal magnitude to object B but in the opposite direction.
Contextualise Newton’s third law to the motion of an eagle flying
Eagle’s wings push air downwards
Air must also push eagle upwards.
Size of force on the air = size of force on the eagle.
The direction of the force on the air (downwards) is opposite the direction of the force on the eagle (upwards).
Explain the action-reaction property details of Newton’s third law
For every action, there is an equal (in size) and opposite (in direction) reaction.
Contextualise Newton’s Third law using a hammer and nail example
When hitting a nail with a hammer, the force of the nail on the hammer is equal to the force of the hammer on the nail.
Forces act in the opposite direction of each other.
What is the simple rule of the gravitation law
there is a force of attraction existing between any two bodies of masses in the universe
What is the detailed gravitation law
force is proportional to both of the masses m1 and m2
force is inversely proportional to the square of the distance, r, between their centre of mass.
how is r measured for the gravitation law
From the centre of mass of one object to the next object (not from surfaces)
what is the gravitation law formula
F = G (m1,m2/r2)
F = G x (m1 x m2)
—————
r^2
What value is G for Newton’s universal law of gravitation
G = 6.673 x 10-^11 m3 kg-1 s-2.
One Newton of force is enough to do what?
one N is the force needed to accelerate one kg of mass at the rate of one m/s2.
What does Newton’s gravitation law provide
This formula gives the magnitude of the force without direction.
How do you determine the centre of mass of a pole
An easy way to determine the location of the centre of mass of a rigid pole is to support the pole horizontally on one finger from each hand.
Gently slide your fingers together. When your fingers meet, you will be at the centre of mass at which time you can easily hold up the pole with only one finger as long as it can withstand the entire weight of the pole.
If an object is uniform/regular, where is the centre of mass
If the object is uniform, a meter stick for example, the centre of mass will be at the exact geometric centre;
If an object is irregular, where is the centre of mass concentrated
if the object is irregular in shape, such as a hammer, the centre of mass will be closer to the heavier end.
Of any object, what kind of property is the centre of gravity
Centre of gravity is a geometric property of any object.
The centre of gravity is also the average location of the weight of an object.
The motion of any object in space can be described in terms of centres of gravity, how
It is
- translation of the centre of gravity of the object from one place to another
- rotation of the object about its centre of gravity if it is free to rotate.
What is free fall motion
vertical motion of an object with reference towards earth.
