P5- forces Flashcards
(37 cards)
what is a scalar quantity and give some examples.
a quantity with only size
-speed, distance, time, mass, temperature
what is a vector quantity and name some examples
a quantity with size and direction
-force, velocity, displacement, acceleration
what is a force
a push or a pull
what is the difference between contact and non contact forces? give some examples of each
contact forces require the objects to be touching for a force to act whereas non-contact forces don’t.
C- friction, resistance etc
NC-magnetic force, gravitational force etc
how can you calculate the weight of an object given you have the mass and gravitational field strength.
weight (N)= mass (kg) x gravitational field strength (N/kg)
what is a resultant force of an object?
the overall force of an object (the amount of force you are left with after adding up all the forces i.e 2N to the left and 6N to the right will create a resultant force of 4N to the right)
what does it mean if the resultant force on an object is in equilibrium?
when all the forces add up to give a resultant force of zero meaning it remains unchanged. (2N to the left and 2N to the right means they cancel out - 0N so the object doesn’t move as forces are balanced)
how could you work out the amount of force applied on a spring
F=KE
force (N)= spring constant (N/m) x extension (m)
how do you measure the link between force and extension? (inc equipment)
equipments: clamp, fixed ruler, spring, hanging masses (multiple)
1. measure natural length of spring
2. add mass to spring- record mass and measure new length of spring. calculate extension (change in length)
3. repeat process for another 5 ish times at least
4. plot graph. if it looks like a curve, that’s if you exceed the limit of proportionality between force and extension.
what is the difference between distance and displacement?
distance is a scalar quantity however displacement is a vector quantity.
what is the difference between velocity and speed
speed is scalar, velocity is vector (speed with a given direction).
describe the typical speed for:
- walking
- running
- cycling
- car
- train
- plane
- walking= 1.5 m/s
- running= 3 m/s
- cycling = 6 m/s
- car = 25 m/s
- train = 30 m/s
- plane = 250 m/s
what does acceleration mean?
how quickly you’re speeding up
how do you calculate acceleration?
acceleration (m/s^2) = change in velocity (m/s) / time (s)
what does uniform acceleration mean
constant acceleration
how to you calculate uniform acceleration
final velocity-initial velocity = 2x(acceleration x distance)
v2 - u2 = 2as
what does friction do and how can you reduce it?
it acts in the opposite direction to movement and therefor slows things down. can be reduced by lubrication.
what is drag and how can you reduce it?
the resistance you get from a moving object. it increases as the speed increases and is reduced by making objects streamlined.
what is terminal velocity?
when the resultant force acting on an object is 0 meaning it is moving at a steady speed.
what is newtons first law?
a resultant force is needed to make something start moving, speed up or slow down.
what is newtons second law?
the larger the resultant force on an object, the more it accelerates- force and direction are directly proportional..
what formula can be used to describe newtons 2nd law?
F= ma
force (N) = mass (kg) x acceleration (m/s^2)
what is newtons 3rd law?
when two objects interact, the forces they exert on each other are equal and opposite.
what is inertia?
the tendency to remain unchanged. so is the tendency to continue in the same state of motion.
