Topic 1 - Motion, Forces and Concervation of energy Flashcards
Whats the difference between weight and mass?
mass has a magnitude but no direction making it scalar whereas weigh is a vector and it has a direction and a size
Whats the difference between displacement and distance
Displacement is vector
Distance is scalar
Whats the difference between Velocity and speed
velocity is a vector speed is scalar
What does accelerating mean
How quickly you are speeding up so change in velocity in amount of time
What does momentum mean
proportion of mass x velocity
it is how much power “oomph” something has to move
How can speed be measured in a lab
How long it takes for someone to walk a set distance
What is the formula relating acceleration
Change in velocity / time
Whats the formula relating acceleration, velocity and distance
velocity^2 - initial velocity^2 = 2 x acceleration x distance
what is the acceleration in free fall
10m/s^2
What is a resultant force
overall force acting on an object in a certain direction
what is the effect of balanced forces on moving and stationary objects
The forces are not balanced on an object which is accelerating but are when an object is stationary
What is the effect of a non-zero resultant force on moving or stationary object
-non- zero forces always produce an acceleration or deceleration in the direction of the force
(this can be in any direction , stopping, starting, slowing or speeding)
What is circular motion at a constant speed
Circular motion causes a constantly changing velocity and therefore an acceleration
What force is needed to keep an object moving in a circular path
A centripetal force
Can you name an example of an object moving in circular motion with a constantly changing velocity
A planet ii orbit
What is the difference between weight and mass
mass is the amount of stuff in an object and is a scalar quanity
weight is a vector and is the force due to gravity
What factors determine an objects weight
gravitational field strength and force surrounding an object
what equation relates Gravitational Potential energy
mass x GFS x change in height
what equation is used to find weight
mass x GFS
How can weight be measured
Newton meter/ calibrated spring balance
what is an acceleration
a changing velocity
What factors effect acceleration
change in speed / time
&
Resultant force/ mass
What is the equation relating the factors in acceleration with resultant force
resultant force / mass
What does inertial mass mean
Ratio of force over acceleration, determines how difficult it is to change the velocity of an object
What does newtons 3rd law state
when two objects interact the forces they exert on each other are equal and opposite
What does newtons 2nd law state
Acceleration is proportional to the resultant force
Force = mass x acceleration
what does newtons 1st law state
an object will continue moving at a constant velocity unless acted on by an unbalanced force
What is an equilibrium situation
when forces acting on each other are equal
what are action reaction pairs?
examples?
-when an object pushes on another object causing an action force
-they feel an equal and opposite force in opposite directions and so accelerate further away from each other
Eg) skaters pushing against each other
What factors effect momentum
mass x velocity
What is the idea of conservation of momentum
total momentum before = total momentum after
Name some examples of momentum in collisions
with car and wall
If a car hits a wall and the wall has momentum of 0 and the car is moving with a velocity then when the car hits a wall it causes the wall to now have a momentum
How can we measure human reaction times
On a computer based test or Ruler drop test
-record distance ruler dropped and time to work out speed
What is the typical human reaction time
0.2 to 0.6 seconds
whats the link between stopping, thinking and braking distances
Thinking distance is the drivers reaction time
Braking distance is distance when brakes are applied
Thinking + Braking = Stopping Distance
What factors effect stopping distance
tiredness
drugs or alcohol
distractions
friction between tires and road eg) icy or wet
What does work done mean
measure of energy transfer when a force moves an object through a distance.
Explain work done with a cars kinetic energy store
energy in a cars kinetic energy store equals the work done by the brakes.
What is the work done formula
force x distance
What factors effect kinetic energy of a moving object
The mass and velocity
How do you calculate kinetic energy
1/2 x mass x velocity^2
What does a large deceleration mean
having a larger force slow an object down in a shorter amount of time.
How can large accelerations be prevented
The force can be lowered by slowing an object down over a longer period
What are the dangers of large decelerations
They cause serious injuries because it requires a large force
How can we decrease impacts of large decelerations in cars
- crumple zones - increase stopping time
- airbags - slow impact
- seatbelts - stretch slightly
What forces are typically involved in road collisions
-Brakes do work on wheels which transfers energy
from kinetic energy store to thermal energy store
-Force causes brakes to overheat due to large deceleration so might not work properly
what does conservation of energy mean
That energy is never created or destroyed but transferred between stores
Name 4 ways energy can be transferred between stores
Mechanically
Electrically
by Heating
by radiation
Give examples of where energy is concerved
when an object is in an enclosed system
-when a pan, gas, oxygen that heat the pan are in their enclosed surroundings.
Give examples of energy being transferred between stores
Kettle boiling water- electrical (by heating) to thermal
Rock off Cliff - GPE (mechanically by gravity) to kinetic
Bat and Ball hitting - kinetic (mechanically) to thermal surroundings by heating
What happens to wasted energy in energy transfers
It is dissipated to surroundings
Which ways can energy be wasted by mechanical processes
whenever work is done mechanically, frictional forces occur and energy is transferred to thermal stores of whatever is doing the work or surroundings
eg) brakes heating
How can we reduce unwanted energy transfers
Lubrication- decreases frictional forces
Insulation - decreases energy transfers by heating
What does efficiency mean and how can it be increases?
Less energy is wasted
-increases with insulation and lubrication by reducing unwanted energy transfers
How do you calculate efficiency
useful energy / total energy x 100
Why does insulating reduce unwanted energy transfers in the home
Insulating walls (It has trapped pockets of air) stops conduction
What does thermal conductivity mean
How well materials transfer heat energy through conduction
what effects does thickness of walls and thermal conductivity of a buildiing have on its rate of cooling
Thicker the wall the slower the rate of energy transfer. The lower the thermal conductivity of the walls the slower the rate of cooling
How do factors effect the gravitational Potential energy stored in an object
mass, height, and GFS
Name some non renewable energy resources
Oil
coal
gas
nuclear
Positives an negatives of non renewables
+more efficient and reliable
- finite resource
- environmental problems : release fossil fuels and oil spills
Name some renewable energy resources
Biofuels, wind, solar, tidal, hydro-electric
Positives an negatives of renewables
+never run out
+lower impact on environment
+no emissions
-less reliable can be weather dependent
Why can we not use only renewable energy sources
because they dont produce as much energy and arent as reliable
eg) solar relies on sun and turbines on wind
