P5 Forces And Motion Flashcards
What is contact force
When objects physically are physically touching
Eg friction, normal contact force, air resistance, tension
What is non contact force
When the objects are not
Eg. Magnetism, electrostatic force, gravity
What is a scalar
A quantity (force) that only has magnitude
What is a vector
A quantity (force) that has magnitude and direction
5 examples of scalars
(D, S, M, E, T)
Distance
Speed
Mass
Energy
Temperature
5 examples of vectors
(D, V, A, F, M)
Displacement
Velocity
Acceleration
Force
Momentum
Weight is the force that ____ pulls an object down with
GRAVITY
Equation linking Weight, Mass and Gravitational Field Strength
Weight (N) = Mass (Kg) x Gfs (N/kg)
GFS of earth
9.8 N/kg
100 grams = how many Newtons
1
Work done means
Energy transferred by a force
What is Hooke’s law
Force and extension are directly proportional
Force = Spring Constant x Extension
What is the practical for springs .
How to avoid a systematic and a parallax error whilst doing it?
-Add masses onto a spring to change force
-Measure extension of spring with a metre ruler at each weight
-Plot Force (weight) against extension.
-Find the gradient of the graph to find the spring constant
-Avoid systematic error by lining up 0cm with bottom of spring
-Avoid parallax error by getting on eye level when measuring
What is the principle of moments
When the sum of clockwise moments = sun of anti-clockwise moments, a system is in equilibrium (will not turn)
What is used to increase moments
Gears
What causes pressure in water
The weight of the column of water above an object, pushing down on it
What causes pressure in a gas
The particles colliding with the walls of the container, exerting a force on them
To increase pressure in a gas you can
(3 things)
Decrease volume of container
-Increase concentration (more frequent successful collisions)
Increase the temperature (more frequent collisions, due to faster speed, AND collide with more momentum, so greater force)
The higher your altitude, the ___ dense the atmosphere becomes, meaning the ____ the pressure
Less, Lower
The gradient of a distance/displacement - time graph gives you the
Speed/velocity
The gradient of a speed/velocity - time graph gives you the
Acceleration
The area under a speed/velocity-time graph gives you the
Displacement
What is the average walking speed
1.5m/s
What is the average running speed
3m/s
What is the average cycling speed
6m/s
S=
U=
V=
A=
T=
Displacement(M)
Initial velocity(M/s)
Final velocity(M/s)
Acceleration (M/s^2)
Time(s)
What is Newtons 1st law
If no resultant force acts on an object, it’s motion will be constant(velocity will not change - terminal velocity)
What is Newtons 2nd law
Force (N) = mass (kg) x acceleration (M/s^2)
What is Newtons 3rd law
For every action (force) there is an equal and opposite reaction(force)
How to do Newtons 2nd law practical
-Accelerate trolley on track with slotted mass on string over pulley
-Use light/photo-gates to measure acceleration
-Change force by removing masses and placing on the trolley (to keep the total mass of the system the sams)
-Plot force against acceleration, gradient = total mass
Stopping distance =
Thinking distance + braking distance
Thinking distance is affected by
-Speed
-Distractions
-Alcohol
-Drugs
-Tiredness
Braking distance is affected by
Speed: if velocity doubles , breaking distance quadruples
Condition of breaks, tires, road
Weather
In any collision, TOTAL MOMENTUM is always
Conserved
Force is a measure of the rate of ____ of _____
Change of momentum
