1) Motion, Forces and Conservation of Energy Flashcards
what is a scalar quantity? examples
size or magnitude but NO direction
-mass, speed, distance , energy
what is a vector quantity? examples?
size or magnitude and HAS direction
-force, weight, velocity, displacement, acceleration, momentum
what is velocity?
speed in stated direction
what is the equation for working out speed?
speed(M/s)= distance m / time s
what is the equation for average speed?
av. speed= total distance / total time
what does a straight line on a graph tell you about he speed?
constant spped
what does a curved line getting stepper tell you about the speed?
accelerating
what does a curved line getting flatter tell you about the speed?
decelerating
what does a flat line tell you about the speed?
stationary
what is the equation for acceleration?
acceleration m/s2 = change in velocity m/s
/ time taken
a=(v-u) / t
what is the equation for velocity?
v2 - u2 = 2 x a x X
X is the distance travelled
what can you interpret from a velocity/ time graph?
- slope or gradient says acceleration
- area under graph gives distance
how do you work out the acceleration on a velocity time graph using the gradient?
acceleration = change in velocity/time taken
how can you use laboratory more accurate equipment to measure speed?
-light gates connected to data logger or computer
what is the typical speed for walling?
1.5m/s
what is the typical speed for running?
3m/s
what is the typical speed for cycling?
6m/s
what is the typical speed for sound in air?
330m/s
what is newtons first law?
- resultant force on stationary object is zero it will stay stationary
- if resultant force on moving object is zero it will stay at same speed and direction
what is newtons first law if the resultant force isn’t zero?
-acceleration/ deceleration
what is the formula which describes newtons second law?
F= m X a force(N)= mass (kg) X acceleration (m/s2)
what is the definition of weight? and what is it measured in?
- force exerted due to mass and GFS
- measured in newtons
what is the equation for weight?
weight= mass X gravity
how is weight measured?
-newtonmeter
what is the relationship between weight and the gravity?
-weight is directly proportional to value of gravity
how would you investigate force and acceleration?
- set up trolly with light gates and ramp
- record different velocity and time for different masses on the trolly
- work out acceleration by dividing velocity by time
- if changing mass slope must stay the same
what conclusion is found after investigating force and acceleration?
-acceleration doesn’t depend on mass and stays similar throughout
what happens to the speed and velocity of an object moving in a circular motion?
- constant speed
- changing velocity
why does circular motion happen? and what force must be acting? example.
- must be a centripetal force
- objects move at right angles to it
- satellite around earth
what is newtons third law?
for every action there is an equal and opposite reaction
how does newtons third law act with equilibrium?
-eg if a man is pushing on a wall but the wall won’t move because the forces in the system are balanced.
how does newtons third aw work with collisions?
- total momentum before equals total momentum after
- if 2 cars collide equal and opposite forces
- both cars
what is the definition of momentum?
product of mass and velocity
what is the equation for momentum and what is it measured in?
p= m X v
kgm/s2
momentum= mass X velocity
what is the definition of force?
rate of change of momentum.
what is the equation for force using momentum?
mv - mu
F= ———-
t
force= change in momentum/ time
what is a way of measuring human reaction times? and what is the formula used?
- ruer drop test
- hold ruler someone drops catch and measure distance
- reaction time= (squ.root) 2 X distance/ gravity
what is the average reaction time for a person to respond to a stimulus?
0.2-0.25 seconds
what is stopping distance of a vehicle the sum of?
thinking distance + braking distance
what are some of the factors which effect stopping distance?
- tired
- alcohol+drugs
- mass of car
- icy or wet conditions
what are some of the factors which could effect a drivers reaction time?
- tiredness
- age
- alcohol
- distractions
what is a danger of large decelerations?
typic forces of 10,000N exhorted on car
what is the formula for change in gravitational potential energy?
GPE= m X g X change in vertical height
what is the formula for kenetic energy?
kE= 0.5 X m X v2
what is meant by conservation of energy?
- can be stored, transferred or dissipated
- not created or destroyed
how is energy changing when a ball is rolled up a slope?
-turns from kinetic energy to gravitational potential energy
how is energy change when a bat hits a ball?
- kinetic energy
- thermal energy
- sound energy
how is energy changed when a rock is dropped from a cliff?
- gravitational potential energy
- kinetic energy
how is energy changed when a car is slowing dow?
- kinetic energy
- thermal energy
how is energy changed when a kettle has boiled water?
- electrostatic energy
- thermal energy
what is the definition of a closed system and what is an example?
- energy can flow in and out
- but no mass change
- pan boiling water, with lid, no steam can escape
how does energy have anything to do with closed systems?
- energy transfers
- no change to total energy
how are mechanical processes wasteful? and give example.
- lead to risen temperature
- energy stored in less useful ways
- light + sound energy from TV absorbed into people rising their temperature
how is energy dissipated? example.
- some usefully transferred some dissipated
- TV giving out heat
what are some of the ways of reducing unwanted energy transfers?
lubrication- reduces friction, therefore reduces thermal energy
insulation- reduces energy transfer by heating, air gaps in walls
what are the effects of thermal conductivity?
- how well material transfers energy
- metal has a high thermal conductivity
- house walls have a low to keep heat in
what is the equation for efficiency?
efficiency= useful energy/ total energy
how can efficiency be increased?
thermal insulation
lubrication
what are the main renewable energy resources?
solar cells bio-fuels - animals and pants tidal power wind turbines hydroelectricity
what are the main non- renewable energy resources?
nuclear fuels
fossil fuels
what are some of the pattern and trends with energy use?
- bio mass remained constant
- mostly used fossil fuels
- huge rise in energy usage
- huge rise in population
- increase in nuclear power
