dynamics part 1 Flashcards
(16 cards)
what is force?
Intuitively, a force is an interaction between objects to explain changes in motion.
what are the types of forces?
- non-contact forces (do not require objects to be in contact )
- contact forces ( between objects that are in contact )
what are the non contact forces?
Gravitational force
The pull exerted by Earth’s gravitya any object (i.e. weight)
Electrostatic force
The attractive (i.e. pull) or repulsive (i.e. push) forces between electric charges
Magnetic force
The attractive (i.e. pull) or repulsive (i.e. push) forces between magnets
what are the contact forces?
Friction
The force that opposes or tends to oppose motion between surfaces in contact
Air resistance
The frictional force exerted by air that opposes the motion of moving objects
Normal force
The push exerted by a surface on an object pressing on it — this push is always perpendicular to the surface
Tension
The pull exerted by a stretched spring, string or rope on an object attached to it
what is mass? what is its SI unit?
Mass is a measure of the amount of matter in a body.
Its Sl unit is the kilogram (kg).
what are some characteristics of mass?
Mass is a property of a body that does not change with its location or shape. The mass of a body depends on the number and composition of atoms and molecules that make up the body. It is a scalar quantity.
what is weight? what is its SI unit?
Weight is the gravitational force acting on an object that has mass.
Its Sl unit is the newton (N).
what are the characteristics of weight?
Since weight is a force, it is a vector quantity with both magnitude and direction. The direction of weight is downward, towards the centre of Earth
what is a gravitational field?
A gravitational field is a region in which a mass experiences a force due to gravitational attraction.
what is gravitational field strength?
Gravitational field strength g is defined as the gravitational force per unit mass placed at that point.
what is the formula for g (gravitational field strength)?
g = w / m
gravitational field strength (N/kg) = weight (N) / mass of the object (kg)
how does gravitational field strength affect the weight of an object? (compare earth : moon)
The weight of an object depends on the strength of the gravitational force acting on it.
weaker gravitational field = object would weigh less
On Earth, the gravitational field strength g is approximately 10 N/kg. on the moon, the gravitational field strength on the moon is 1.6 N/kg.
This means that an object on Earth’s surface experiences a greater force than on the moon’s surface, and would weigh much more on Earth’s surface than on the moon’s surface even though its mass remains unchanged as earth has a higher gravitational field strength acting on it.
what is the relationship between weight and mass?
w = mg
what is Gravitational Field Strength and Acceleration Due to Gravity?
W = m * 10N/kg
F = ma
W = m * 10m/s2
By comparing equations (1) and 2), we can see that gravitational field strength near the
= 10 N/kg) is equivalent to the acceleration of free fall (g = W
what are some common weighing instruments?
weight - spring balance, (electronic balance)
mass - beam balance
what is the difference between mass and weight ?
Mass
an amount of matter
a scalar quantity (i.e. has only magnitude)
SI unit: kilogram (kg)
independent of the gravitational field strength
measured with a beam balance or a calibrated electronic balance
Mass
Weight
a gravitational force
a vector quantity (i.e. has both magnitude and direction)
Si unit: newton (N)
dependent on the gravitational field strength
measured with a spring balance
