P5 Forces Flashcards
what are the two components of a vector
magnitude and direction
D A M V F
what are the vector quantities
force,velocity,displacement,acceleration, and momentum
S T T D M
what are the scalar quantities
speed,distance,mass,temperature,time
what is the relationship between mass and weight
they are directly proportional
what is work done
when a force moves an object through a distance
how do you know if an obejct is in equilibrium
if the forces are balanced
what is the difference between elastic and inelastic deformation
if an object has been elastically deformed it can go back to its original shape and length after the force has been removed. if an object has been inelastically deformed it doesn’t go back to its original shape after the force has been removed.
what is the relationship between extension and force
they are directly proportional
what is the limit of proportionality
the limit to the amount of force you can apply to an object for the extension to keep on increasing proportionally. it is shown on a graph on a point marked P.
what is the method for the extension of a sting practical
1) measure the natural length of the string (when no load is applied) with a millimetre ruler clamped to the stand. make sure you take the reading at eye level and add a marker to the bottom of the string to make it more accurate.
2) add a mass to the string and allow it to come to rest. record the mass and measure the new length of the sting. the extension is the change in the length
3) repeat this until you have added at least 6 weights to the string
4) plot the results on a force-extension graph
what is a moment
the turning effect of a force. a larger force or a larger distance would mean a larger moment.
how do you get the maximum moment of a force
push at right angles
how do you know if an object is balanced
if the total anticlockwise moment equals the total clockwise moment about a pivot
what do levers do
levers increase the distance from the pivot at which the force is applied. this means that levers make it easier to do work
what happens when a fluid is fully submerged in water
the pressure of the fluid exerts a force on it from every direction. pressure increases with depth,so the force exerted on the bottom of the object is larger than the force acting on the top of the object. this causes a resultant force, also known us upthrust.
what happens when the weight of an object is equal to the upthrust
the object floats because the forces are balanced. if the weight is greater than the upthrust then the object will sink. this means that whether or not an object will sink or float, depends on its density
what happens when an object is less dense than the fluid it is in
it displaces a volume of fluid that is equal to its weight before it is completely submerged, at this point the weight is equal to the upthrust so the object floats
what happens to atmospheric pressure when the height is increased
the atmospheric pressure has decreased, this is because as the altitude increases, the atmosphere gets less dense so there are fewer air molecules that are able to collide with the surface.
is distance a scalar or a vector quantity
scalar
is displacement a scalar or a vector quantity
vector
is speed a scalar or a vector quantity
scalar
is velocity a scalar or a vector quantity
vector
what are the average speeds for:
a person walking
a person running
a person cycling
a car
a train
a plane
a person walking - 1.5m/s
a person running - 3m/s
a person cycling - 6m/s
a car - 25m/s
a train - 55m/s
a plane - 250m/s
what is acceleration
the rate of change of velocity. negative acceleration is known as deceleration, when this happens you are slowing down instead of speeding up.