Chapter 1/2 - Forces and motion Flashcards
What was Newton’s first law?
That a body will remain in its present state of motion unless an external force acts upon it
What is Newton’s second law?
That force= mass x acceleration
This can be rearranged to a= f/m
It shows if the force increases so does the acceleration
What is Newton’s third law?
That every force has an equal and opposite reaction
What is the equation for speed? What is another one for the final velocity(for velocity/ speed)?
S = d/t V= u + at V2= u2 + 2as
What is the Earths gravity?
10 (9.81) m/s
What do all the parts in SUVAT mean?
S = distance / displacement U = initial velocity V = final velocity A = acceleration T = Time
What is the equation for acceleration?
A = (v-u)/t
In a distance time graph what does a horizontal line represent? What about a diagonal straight line?
In a distance time graph a horizontal line is when the object is stationary. A straight diagonal line is when the object is travelling at a constant speed.
In a distance time graph what does the gradient show?
The speed the object is moving
In a velocity time graph what does a horizontal line mean? What about a diagonal line?
In a velocity time graph a horizontal line shows the object moving at a constant speed. A diagonal line shows the object is accelerating
Give 3 equations to show the distance traveled
D= s x t S= ut + 1/2 at2 S= 1/2(u+v)t
What is acceleration?
The rate of change of velocity
What are the 2 types of velocity? Which does gravity effect?
Vertical and horizontal velocity, gravity effects the vertical velocity
What is momentum? What is its equation?
Mass x velocity, it’s conserved and passed on from one object to another, it is a vector
What is a vector?
Something that has both magnitude and direction
Eg 5 miles North, 30m/s East
What is the total momentum equation?
Total momentum before collision= total momentum after a collision
What happens to the momentum if the mass doubles?
The velocity halves
When 2 objects are pushed apart from stationary, 0ms, what is the momentum afterwards if they are both pushed away with the same force?
One would be of negative charge and the other positive so the total momentum afterwards would still be the same
What is the equation for the increase in momentum?
M x v - m x u OR m(v-u) m being mass
What is the equation for the rate of change in momentum?
m(v-u)/t
Where t is time taken for change to happen
The mass has to be involved otherwise it is the equation for acceleration
What is work done and energy transfer measured in?
Joules
What effects work done?
The force applied and the distance moved in direction of that force, such as how many books you carry in a bag and how far you travel with that effects how much energy/ force you use
What is the equation for work done?
Force applied x distance moved in direction of force
What is 1 joule of energy/ work done?
When 1 newton of force moves through one metre, if you pull a box with a steady force of 25N 3m you have done 75 Joules of work (3x75), this would have been transferred as heat and friction if it was on a rough ground
What is weight and it’s equation?
A force measured by
The mass of an object x the gravitational field strength (10N per kg on Earth)
What would a 4kg mass weight be on Earth?
40N
How fast is a verhole moving if the force from air resistance/ friction is equal to the forward force from the engine?
At a constant velocity
What is thinking distance?
The distance a vehicle will travel in the time it takes the driver to react, this can be the difference between having an accident and not
What is a key part in the thinking distance?
The drivers reaction time
How will the speed the vehicles travelling at effect the thinking distance? Why?
If the vehicle is moving faster the thinking distance will be further, because whilst the driver is reacting the vehicle is still moving at that speed, so if this is faster it will go further during the drivers reaction time
Name some things which would increase the reaction time of the driver
The radio/ music, chatting, looking away at something, being under the influence of drugs or alcohol, tiredness, being ill
What are the legal limits for the amount of alcohol a person can have in their system whilst driving?
35 micrograms/ 100ml breath
OR 80 micrograms/ 100ml blood
What are the speed limits in the UK? What are these for?
30 mph in built up areas - 70 mph on dual carriageways and motorways because the higher the speed during accidents the higher the death rate, especially with children
What is a scalar?
Something that have just a size
Eg 5m, 4000 calories
Is displacement a vector or scalar?
Vector, how far something has moved from where it started in a straight line, how far out it is
What is distance?
A scalar quantity which means how much ground an object has covered in its movement
How is speed and velocity different?
Speed is a scalar quantity, how fast an object is moving, whereas velocity is a vector quantity and it represents the rate at which an object changes position , m/s and direction
What is the equation for average velocity?
Displacement / time
What is the definition of force?
The push or pull upon an object resulting from interacting with another object
What is the definition of mass?
Scale quantity, the amount of a substance
What is the definition of weight?
A vector quantity, forces acting on a mass due to gravity
What is the definition of momentum?
A vector quantity describing a mass in motion
