Key Words - motion and forces Flashcards
acceleration
how quickly velocity changes. positive if speeding up, negative if slowing down
balanced forces
when the forces in opposite directions on an object are the same size so that there is a zero resultant force
resultant force
the total force that results from two or more forces acting upon a single object. it is found by adding together the forces, taking into account their directions
scalar quantity
a quantity that has a magnitude (size) but not a direction.
speed
how fast something is moving
unbalanced forces
when the forces in opposite directions on an object do not cancel out, to there is a non-zero resultant force
vector quantity
a quantity that has both a size and a direction
examples of scalar quantity
mass, distance, energy and speed
examples of vector quantity
force, velocity, displacement, momentum and acceleration
velocity
the speed of an object in a particular direction
centripetal force
a force that causes objects to follow a circular path. the force acts towards the centre of the circle
mass
a measure of the amount of material there is in an object
weight
the force pulling an object downwards
gravitational field strength
a measure of how strong the force of gravity is somewhere
inertial mass
the mass of an object found from the ratio of force divided by acceleration
action - reaction forces
pairs of forces on interacting objects. they are always the same size, in opposite directions, and acting on different objects
balanced forces
forces acting on the same object. balanced forces are always equal, in opposite directions, and always act on the same object.
equilibrium
when a situation is not changing because all the things affecting it balance out
conservation of momentum
the total momentum of moving objects before a collision is the same as the total momentum afterwards, as long as no external forces are acting
momentum
the mass of an object multiplied by its velocity.
what type of quantity is momentum
vector quantity
thinking distance
the distance travelled by a vehicle while the driver reacts
braking distance
the distance by a vehicle while the brakes are working to bring it to a halt
stopping distance
the distance in which a car stops, which is the sum of the thinking and braking distance
reaction time
the time taken to respond to a stimulus
stimulus
something outside the body that can be detected by the body, such as a sight or sound
response
the way the body reacts to a stimulus
crumple zone
a vehicle safety device in which part of the vehicle is designed to crumple in a crash, reducing the force of the impact
deceleration
slowing down - a negative acceleration
