Forces and motion Flashcards
What is a vector quantity
Forces that have a magnitude and a direction
Examples of vector quantities
Force,velocity,acceleration,momentum
What is a scalar quantity
Quantities with a magnitude but no direction
Scalar quantity examples
Speed distance mass temperature
What is a contact force
When 2 objects have to be touching for a force to act
Examples of contact force
Air resistance
Tension in ropes
What is non contact force
When two objects do not need to touch for a force to apply
Examples of non contact forces
Magnetic force
Gravitational force
What is the difference between mass and weight
Mass is just the amount off stuff in an object while weight is the force acting on an object due to gravity
What is the equation for weight
Weight = mass x gravitational field strength
What is resultant force
If you have a number of forces acting at a single point you can replace it with a single force .
This single force is called the resultant force
What is the work done equation
Force x distance
Energy transferred is the same as work done
What is the equation that links force and spring constant
Force=spring constant x extension
What is the equation for elastic potential energy
Elastic potential energy = 0.5 x spring constant x extension2
What is a moment
A moment is the turning effect of a force
What is the equation of a moment
Moment = force x distance
What is the equation for pressure
Pressure = force/area
What is density the measure of
Measure of compactness of a substance i.e how close the particles in the substance are
How do you calculate pressure at a certain depth
Height of the column x gravitational field strength x density of liquid
What do objects experience when in a liquid
They experience upthrust
When the object is submerged the pressure of the fluid exerts a force from every direction
Why does an object balance
When the upthrust is equal to the objects weight
What happens when an object is denser than the liquid it is placed in ?
It is unable to displace enough fluid to equal it’s weight meaning it’s weight larger than the upthrust causing to to sink
What is atmospheric pressure
The layer of air that surrounds the earth
Why does atmospheric pressure decreases as we increase altitude
Atmosphere gets less dense so there are fewer air molecules
Why is displacement a vector quantity
Measures the distance and direction in a straight line from an objects starting point to finishing point
What is acceleration and how is it calculated
Acceleration is the change in velocity over a period of time
Change in velocity divided by time
What is the equation that links final velocity and initial velocity
Final velocity 2 - initial velocity 2=2(acceleration x distance)
What is drag
The resistance you get in fluids (gas or liquids)
For example air resistance is a drag
How does an object reach terminal velocity
When an object first sets off the force of gravity is much more than the frictional force slowing it down so it accelerates . Over time these 2 forces will begin to balance out . (Acceleration force=frictional force) this causes an object to reach it’s maximum speed
(Terminal velocity)
What does newtons first law state
A resultant force is needed to make something start moving , speed up or slow down .
How do you calculate resultant force
force =Mass x acceleration
What is inertia
Until acted upon objects that are stationery will remain that way and objects at a steady speed will also remain that way . The same state of motion is called inertia
How do you calculate inertia
Mass = force / acceleration
What is newtons third law
When 2 objects interact the forces they exert on each other are equal and opposite
How do you calculate stopping distance
Thinking distance + braking distance
Name factors that effect braking distance
Weather or road surface
Condition of tyres
Condition of brakes
Energy transfer when when the brake pedal is pushed
When the brake pads are onto the wheels friction occurs
This causes work to be done ,the work done between the brakes and the wheels transfer energy from the kinetic energy stores in the wheels to the thermal stores of the brakes . This causes the brakes to increase in temperature
Equation for momentum
Mass x velocity
What is the conservation of momentum
In a closed system the total momentum before an event is the same after the event
What is the equation for change in momentum
Force = change in momentum/change in time
What safety features do cars have that help in a crash
Crumple zones-crumple on impact increasing the time it takes for the car to stop
Seat belts-stretch increasing the time taken for the wearer to stop
Air bags - inflate before you hit the dash board of a car, the compressing air inside it slows you down more gradually
Newtons second law
Acceleration of an object depends on the mass of the object and the amount of force applied