Forces Flashcards
what is a scalar quantity
only has a size (magnitude)
what is a vector quantity
has both magnitude and direction
what is a force
a push or pull that acts on an object due to the interaction with another object
is force vector or scalar
vector
what is a contact force
when objects are physically touching e.g friction, resistance and tension
what is a non contact force
when objects are physically separated e.g gravitational, electrostatic and magnetic
what is the same about the interaction pair of forces when two objects interact with each other
the forces are the same size
what is different about the interaction pair of forces when two objects interact with each other
forces are in opposite directions
what is the size of the resultant force on an object if the forces on it are balanced
0
what is the name for the force acting on an object due to gravity
weight
what instrument can be used to measure the weight of an object
calibrated spring balance (newtonmeter)
what is the centre of mass
the point through which the weight of an object can be considered to act
what is elastic deformation
an object can go back to its original shape and size when deforming forces are removed
what is inelastic deformation
an object can’t go back to its original shape and size when deforming forces are removed
how do you find the spring constant from a force-extension graph of a spring
find the gradient of the straight line section
what is the turning effect of a force called
moment
what can you say about clockwise and anticlockwise moments on a balanced object
sum of all clockwise moments = sum of anticlockwise moments
how does a lever reduce the amount of force needed to create a particular sized moment
by increasing the distance from the pivot
what happens to the moment of a force when a small gear drives a large gear
moment is increased
what is a fluid
a substance that can flow - liquid or gas
why does the pressure of a liquid increase with depth
pressure at any point in a liquid is due to the weight of liquid above that point
why does the pressure in a liquid depend on the density of the liquid
pressure is due to the weight of the liquid, and weight of the liquid depends on its density
what is upthrust
the resultant force due to the difference in pressure between the top and bottom surfaces of an object submerged in a fluid
what will an object placed in a fluid do if its weight is equal to the upthrust
float
what will an object placed in a fluid do if its weight is greater than the upthrust
sink
why does an object that is more dense than a fluid sink if its placed in the fluid
weight of the object is greater than the weight of the fluid displaced so the weight of the object is greater than the upthrust
why does an object that is less dense than a fluid float if its placed in the fluid
weight of the object is less than the weight of the fluid displaced so the weight of the object is less than the upthrust
does an object that is partially submerged in a fluid experience a greater pressure on its bottom or top surface
bottom
what is the earths atmosphere
the layer of air that surrounds the earth
what is atmospheric pressure caused by
air molecules colliding with the surfaces
why does atmospheric pressure decrease with increased altitude
the density of the air decreases, fewer air molecules as you go higher - there is less weight of air above a surface and fewer air molecules so density of the atmosphere decreases
how does the height of the atmosphere compare to the radius of the earth
its smaller
what is the difference between distance and displacement
distance is scalar but displacement is vector
what is the difference between speed and velocity
speed is scalar but velocity is vector
what factors can affect the speed at which someone walks, runs or cycles
age, fitness, terrain, and distance
what are the typical speeds for a person walking, running and cycling
1.5 m/s, 3 m/s, 6 m/s
what is the typical speed for sound travelling in the air
330 m/s
what is acceleration
change in velocity of an object per second
what is the unit for acceleration
m/s2
how can an object be accelerating even if its travelling at a steady speed
if its changing direction
what is happening if an object has a negative acceleration
its slowing down
what information does the gradient of the line in a distance time graph provide
speed
what information does the gradient of the line in a velocity time graph provide
acceleration
how can the distance travelled by an object be found from its velocity time graph
area under the graph
what is the name for the steady speed a falling object reaches when the resistive force is equal to its weight
terminal velocity
what is the general name for the frictional forces an object experiences when moving through a fluid
drag
in which direction does the drag on an object always act
in the direction opposite to which its moving
what happens to the drag on an object as its speed increases
the drag increases
what can be done to reduce the drag on an object
streamlining
what is inertia
the tendency an object has to remain in a steady state
what is Newtons first law
the velocity of an object will only change if a resultant force is acting on it
what is the resultant force on a stationary object
0
what is the resultant force on an object moving at a steady speed in a straight line
0
what will an object experience if the resultant force on it is not zero
acceleration/ change in velocity
what forces are balanced when an object travels at a steady speed
resistive forces = driving force
according to Newtons second law what is the acceleration of an object inversely proportional to
mass
what does Newtons third law say
when two objects interact they exert equal and opposite forces on each other
starting to move, stopping moving, speeding up, slowing down and changing directions are all examples of what physical process
acceleration/ change in velocity
what is the name given to the distance a vehicle travels to safely come to a stop after the driver has spotted a hazard
stopping distance
what is thinking distance
the distance vehicle travels during drivers reaction time
what is braking distance
the distance vehicle travels once brakes have been applied
what is the relationship between stopping distance, thinking distance and braking distance
stopping distance = thinking distance + braking distance
does the speed of a vehicle have a bigger effect on braking distance or thinking distance
braking
which distance is proportional to the speed of a vehicle
thinking
which distance increases by an increasing amount as speed increases
braking
what are 3 factors that can affect the braking distance of a vehicle
speed, road conditions and condition of tyres and brakes
what is the definition of one joule of work
the work done when 1N of force causes 1m displacement
why does the temp of a vehicles brakes increase when the brakes are applied
work done by the frictional force between the brakes and the wheels transfers energy from the kinetic energy store of the car to the thermal energy store of the brakes
what can happen if the braking force used to stop a vehicle is very large
brakes may overheat
what is the law of conservation of momentum
in a closed system the total momentum before an event is equal to the total momentum after it
how is the force acting on an object related to its momentum
force acting on an object = rate of change of momentum
what are examples of everyday safety features which work by increasing the time taken for the change in momentum
air bags, seat belts, crumple zones in cars, cycle helmets, crash mats
