forces
resultant forces
a resultant force is a force that is produced in a certain direction due to a combination of forces
if the resultant force is zero the object will remain stationary
if the resultant force is not zero the object will accelerate in the direction of the resultant force
newtons 3rd law
every action had an equal (same size) and opposite (in direction) reaction
weight
weight is a force
weight is measured in newtons
weight is a force an object exerts due to its mass and the pull from the gravitational field the object is in
mass
mass refers to the amount of a substance- the amount of matter in a substance/object
it is measured in kilograms
acceleration
it is measured in metres per second squared
acceleration refers to an objects change in velocity (either getting faster or slower)
equations
force= spring constant x extension
moentum= mass x velocity
weight= mass x gravational field strength
velocity= speed/ time
acceleration= change in velocity/ time
force= mass x acceleration
work done= force x displacement
newtons 2nd law
newtons second law is that the acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object
velocity time graph
decreasing straight line= decreasing speed, decelerating
flat line= constant speed
increasing straight line= increasing speed, acceleration
scalars and vectors
vectors
scalars
the size of a quantity is called its magnitude
examples of scalars are volume, density and time
examples of vectors are displacement, velocity and force
a vector can be represented with an arrow. this is because the length of the arrow indicates the magnitude of the vector
physical quantities that have size (magnitude) but no direction are scalars
physical quantities that have size ( magnitude) and direction are vectors
newtons first law
if the resultant force acting on an objecr is zero and:
the object is moving- the object will continue to move at the same speed and in the same direction
the object is stationary- the object will remain strationary
momentum
a moving object has momentum
this is the tendency of the object to keep moving in the same direction
stopping distance
the stopping distance is the distance it takes to stop a moving car
it is divided into two factors: the thinking distance and the breaking distance
contact and non contact forces
thinking distance
Forces are categorised into two groups
Forces either push or pull on an object. This is as a result of its interaction with another object.
contact force
non contact forces
the objects are touching e.g. friction, air resistance, tension and
contact force.
the objects are not touching e.g. gravitational, electrostatic
and magnetic forces.
thinking distance is the distance the car travels between a hazard appearing and the driver applying the brakes
factors that may affect the thinking distance are:
how fast the car is going, how intoxicated the person driving is ( drink and drugs),Concentration of the person, poor visibility