Forces Flashcards
what is a scalar?
quantity with magnitude only
what is a vector?
quantity with both magnitude and direction
what is distance?
how far an object moves (m) - scalar
what is displacement?
distance an object moves, measured in straight line from start point to end point and in the direction of that line - vector
what is speed?
distance an object moves per second (m/s) - scalar
what is velocity?
speed in a given direction (m/s)- vector
what is the resultant force?
overall force acting on an object
the steeper a distance time graph; ….
the faster the motion
what does a horizontal line on a distance time graph mean?
the object is stationary
what does a a curved line on a distance time graph mean?
the object is accelerating or decelerating
the steeper a velocity time graph;…
the greater the acceleration
what does a horizontal line on a velocity time graph mean?
the object is at a constant velocity
what does a a downward sloping line on a velocity time graph mean?
the object is decelerating
what is the gradient on a velocity time graph?
acceleration
what is the area under the line on a velocity time graph?
displacement
how do you calculate velocity?
displacement / time.
all objects with ____ produce a gravitational field.
mass
what gives an object a greater gravitational field?
a greater mass
what is weight?
force acting on an object due to gravity (N)
what happens When a force acts on an object?
the object may change shape by bending, stretching or compressing - or a combination of all three shape changes.
what is A change in shape called?
deformation
what happens to elastic deformation when the force is removed?
it is reversed
what happens to inelastic deformation when the force is removed?
it is not fully reversed when the force is removed - there is a permanent change in shape
what is hooke’s law?
force (N)= spring constant (N/m) × extension (m)
what is the spring constant?
a measure of the stiffness of a spring up to its limit of proportionality.
what is the limit of proportionality?
the point beyond which Hooke’s law is no longer true when stretching a material
what is the elastic limit of a material?
the furthest point it can be stretched or deformed while being able to return to its previous shape.
when does a moment occur?
when a force is applied at a distance from a pivot
how do you calculate a moment?
force x distance
for an object at equilibrium, the sum of the clockwise moments = ?
the sum of the anticlockwise moments
what is the centre of mass?
the point at which the mass can be thought to be concentrated - the point from which the weight of an object acts
if an object is stable, where will the line of action fall?
inside the base
do big gears have a bigger or smaller moment?
bigger - as the distance to the pivot is greater
do big gears rotate at higher or lower speeds than small gears?
lower
what happens in low gear?
a small gear turns a larger gear which gives a low speed and high turning effort
what happens in high gear?
a large gear turns a smaller gear which gives a high speed and low turning effort
what is a fluid?
anything which can flow
how do you calculate pressure?
force / area
what is pressure measured in?
pascals, Pa, or N/m^2
how do you calculate pressure due to a column of liquid ?
density of liquid x height of column x strength of gravity
what is upthrust?
the upwards force which acts on an object in any fluid, which occurs because the pressure at the bottom of the object is greater than the pressure at the top; if the upthrust is bigger than the weight, the object will rise
what is stopping distance?
thinking distance + braking distance
what are some factors that affect thinking distance?
- age
- alcohol
- drugs
- distractions
- speed
- tiredness
what are some factors that affect braking distance?
- mass of car
- speed
- road surface
- condition of brakes
what is braking distance proportional to?
speed of vehicle^2
what is newton’s first law?
objects stay at rest or move with constant velocity unless acted upon by a resultant force
what is newton’s second law?
f = m a
what is newton’s third law?
when two objects interact, they exert an equal and opposite force on each other
what is acceleration?
change in velocity of an object over time (m/s^2)
what is inertia?
tendency of objects to continue in uniform motion
what happens at terminal velocity?
the object moves at a steady speed in a constant direction because the resultant force acting on it is zero.
what are the three stages as an object falls through a fluid?
- at the start, the object accelerates downwards due to the force of gravity
- as the object’s speed increases, frictional forces such as air resistance or drag increase
- at terminal velocity, the weight of the object due to gravity is balanced by the frictional forces, and the resultant force is zero
how do you calculate momentum?
mass (kg) x velocity (m/s)
what is the principle of conservation of momentum?
in a closed system, the total momentum before the event is equal to the total momentum after. if momentum is not conserved in an event such as a collisions it is because external forces are acting on the objects
