P-5 Forces Flashcards
- What is a vector quantity
- Have magnitude and associated direction
- Force is a vector quantity
What is a scalar quantity
- Only have magnitude no direction
- Speed, distance
How are vectors represented
- Represented usually by an arrow
- length of arrow represents magnitude and direction shows direction
What are contact forces
- Objects are touching for the force to act
- friction, air resistance, tension and normal contact
What are non-contact forces
- Objects that do not need too be touching for force to act
- e.g magnetic, gravitational and electrostatic
What is a force
- A push or pull that acts on an object due to the interaction with another object
- Vector
What happens when objects interact
- There is a force produced on both objects
-
What is an interaction pair
- Paire of forces that are equal and opposite and act in two interacting objects
What is weight
- The force acting on an object due to gravitational field around earth
What does weight depends on
- Gravitational field strength
What is the equation for weight
Weight = Mass x gravitational field strength
W = m g
weight in newtons
Directly proportional
What are the two effects of gravity
- Makes all things fall towards ground
- Gives things weight
- What is a centre of mass
- When the weight of an object is considering to act at a single point
- A point where the whole mass is concentrated
How is weight measured
- Using a calibrated spring balance
- A newtonmeter
What is a resultant force
- ## When a number of forces are acting on an object are replaced by a ginned force that has the same effect as all the force as all the other forces acting together
How do you calculate the resultant forces that act in a straight line
- Add the forces that go in the same direction and subtract that which go in the other direction
What are free body diagrams
- Sizes of arrows show relative magnitudes
- Directions are those which re true
What is work done
- When a force causes an object to move through a distance work is done
- Force does work on an object when the force causes a displacement of the object
- What is the equation for work done
- Work done = force time distance
Work done- joules
Force- newtons
- Distance meters
W= F s
What is a joule of work done
- When of force of one newton causes displacment of one meter
- 1 joule = 1 newton meter
- What energy is transferred in one work done
- Energy transfers from one store to another
e. g- electric to kinetic
What effect does work done have affect frictional forces
- Frictional forces acting on an object when met with work done cause the temperature to rise
How can scale drawings be used to find resultant forces
- Draw all forces acting on object tip to tail
- Draw straight line from start of force to end of last one
- mEasure and angle for direction
-why does more than one force have to be acting on an object to stretch compress or bend
- You apply a force
- More than one force needs to acting or else it would just mov in a direction
- What is the difference between elastic deformation and inelastic deformation
- Elastic0 it can go back to original shape ice force removed
- Inelastic
- Cannot return to original shape
What is the proportion of the extension of an elastic object
- The extension of an elastic object, such as a spring, is directly proportions long as the limit of proportionality is not exceeded
What is the equation for force
Force = spring constant x extension
Force- F - newtons
- Spring constant- k- newtons per meter
- Extension - e- meters
What is the relationship between elastic potential and work done
§- Unless inelastically deformed , they are equal
- What are the steps in testing link between force and extension
- Measure natural length - on stand
- Take at eye level - Add mass and allow to come to mess- record length
_ Repeat until more than 6 results have been taken
_Plot
0 when bends- limit of proportinality
- Wheat is the equation for calculating extension
Elastic potential= 1/2 Spring constant x exertion 2
E= 1/2KE2
What are distance and vector
- Distance is how far an object has moved- scalar
- Displacement is distance and direction0 Scalar - Starting point to finishing point
What are speed ad velocity
- Both how fast you are going
- Speed is just how fast
- Velocity is speed in given direction
What is the equation for distance traveled
- Distance+ speed x time
s=vt
What are typical everyday speeds
- Person walking- 1.5m/s
- Running- 3 m/s
- Cycling- 6m/s
- Car-25m/s
- Train-30m/s
- Plane250m/s
- What things can effect speed
- Temperature
- Pressure
- resistance
What is acceleration
- How quickly you are speeding up
- Constant- speeding up air uniform rate
What is the equation for measuring equation
Acceleration- = Change in velocity // time
a=/\v//t
How do you calculate uniform acceleration
- Final velocity2- Initial velocity2 = 2x acceleration distance
v2-u2 = 2as
- What is friction
- Friction always slows things down
- Acts in opposite direction to movement
- TO be at steady speed- have to balance
- Contact force
- Reduced using lubricant
- What is drag
- Drag is resistance found in fluid- gas or liquid
- Streamlined stops drag
- Frictional force sin fluids always increase with speed
What is terminal velocity
- When falling object sets off- gravity much than frictional force
- As speed increases friction builds up
- Gradually reduced the acceleration until the frictional force is equal to acceleration
- It will have reached its terminal velocity
What does terminal velocity depend on
- Less streamlined objects have lower TV
- ## Large surface area- low TV
What is Newtons first law
- Resultant force is needed to make something , start moving, speed up our slow down
- Balanced to be moving at constant pace
What is Newtons second law
- The larger the resultant force the more the object accelerates- directly proportional
- Acceleration will also be interlay proportional to mass - Object with larger mass will accelerate less
What formula can be used to describe newtons second law
- Resultant force= Acceleration x mass
F= ma
What is newtons Third law
- When two object interact the forces they exert on each other are equal and opposite
What is inertia
- Inertia is the tendency for motion to remain unchanged
- ## Until acted upon objects stay at rest
What is inertial mass
- Measures how difficult it is to change the velocity of an object
- M- F//a
Internal mass is a ratio of force over acceleration
- How do you investigate newtons seined law
- Set up set- Trolley- starting line- card in trolley- Light gate- hook of known mass on the end
- Weight of hook and any masses with give acceleration
- Place at starting line and re;are
- Record acceleration given by light gate
- Repeated and get average acceleration \
- Effect of mass- trolley
- Effect of force- hook
What is a stopping distance
- Thinking distance+ Braking distance
- What are thinking and breaking distance-
- Thinking- How far it travels in reaction time
- Breaking- Time it takes to stop under breaking force0 Car - 30mph- 14m - 60mph-55m 70mph-75m
What factors effect Stopping distance
- Thinking - Speed- Reaction time
Breaking
- Speed
- Weather// Road surface- Wet
- tyre condition -
- Break condition
What does breaking rely on
- Friction between breaks breaks
- Faster- more kinetic energy More work needed to stop it
- Larger breaking force means larger deceleration
What is momentum
- Momentum is mainly about how much oomph something has
- Velocity+ mass
- Vector
What is the equation for momentum
- Momentum = mass x velocity
p=mv
What is conservation of momentum
- In a closed system, The total momentum before is the same as after
- If momentum is zero at start it will end as zero
