P5-Forces
0.0(0)
Studied by 2 people
Learn
Practice Test
Spaced Repetition
Match
FlashcardsCard Sorting
1/39
Earn XP
Description and Tags
Study Analytics
Name | Mastery | Learn | Test | Matching | Spaced |
|---|
No study sessions yet.
40 Terms
1
New cards
Vector quantity
Magnitude + direction
Vector Quantities:
* Force
* Velocity
* Displacement
* Acceleration
* Momentum
Vector Quantities:
* Force
* Velocity
* Displacement
* Acceleration
* Momentum
2
New cards
Scalar quantity
Only have magnitude
scalar quantities:
* speed
* distance
* mass
* temperature
* time
scalar quantities:
* speed
* distance
* mass
* temperature
* time
3
New cards
Contact and Non- contact forces
A force is a push or a pull on an object that is caused by it interacting with something
* Contact
\-friction
\-air resistance
\-tension in ropes
etc
* Non contact
\-Magnetic force,
\-gravitational force
\-electrostatic force
etc
* Contact
\-friction
\-air resistance
\-tension in ropes
etc
* Non contact
\-Magnetic force,
\-gravitational force
\-electrostatic force
etc
4
New cards
Interaction pair
When two objects interact there is a force produced on both objects. An interaction pair is a pair of forces that are equal and opposite and act on two interacting objects.
\
The sun and earth are attracted by the gravitational force which is a non contact force
An equal but opposite force of attraction is felt by both sun and earth
A chair exerts a force on the ground, the ground pushes back at the chair with the same force. Equal but opposite
\
The sun and earth are attracted by the gravitational force which is a non contact force
An equal but opposite force of attraction is felt by both sun and earth
A chair exerts a force on the ground, the ground pushes back at the chair with the same force. Equal but opposite
5
New cards
Gravitational force
The force between masses
\-gravity attracts all masses
\-the bigger the stronger forces of attraction which is only really noticeable in planets
Gravity makes all things fall to the ground and gives everything a weight
\-gravity attracts all masses
\-the bigger the stronger forces of attraction which is only really noticeable in planets
Gravity makes all things fall to the ground and gives everything a weight
6
New cards
Gravitational field strength
\-Varies with location
\-the closer it is to the mass causing the field the stronger the gravitational field strength is
\-the closer it is to the mass causing the field the stronger the gravitational field strength is
7
New cards
Centre of mass
Forces of gravity work on a single point the centre of mass where the whole mass is concentrated
8
New cards
Newton meter
Measures weight (N) also a spring balance can measure weight
9
New cards
Equation for weight
Weight (N)=Mass (kg) x Gravitational Field Strength (N/kg)
10
New cards
Resultant force
Left - Right and up-down
11
New cards
Equation for work done
Work done (J)= F (N) x s (distance moved (m))
12
New cards
Finding resultant force
Draw all forces acting on the object from tip to tail and use Pythagoras by joining the lines up
13
New cards
Equilibrium in force
An object is in equilibrium if the forces are balanced
14
New cards
Resolving awkward forces
split into horizontal and vertical components
15
New cards
Stretching, compressing and bending
2 or more transfers of energy into an object at once causing one of these effects to occur
An object which has been elastically deformed can go back to its original shape and length after the force has been removed.
An object which has been inelastically deformed doesn’t return to its original shape
An object which has been elastically deformed can go back to its original shape and length after the force has been removed.
An object which has been inelastically deformed doesn’t return to its original shape
16
New cards
Extension
F(N)=k (N/m) x e (m) (K= stiffness of the material stretching)
17
New cards
Change in proportionality of extension
Known as the limit of proportionality after the amount of force reaches a certain threshold extension is no longer proportional to force.
18
New cards
Extension practical
Calculate weight of masses used through W=mg
Test weights by using identical spring and see if the increase of extension after each weight is added stays the same up to at least 5 weights if it is you need to uses lighter weights or you won’t get enough measurements for your graph
1. Measure the natural length of the spring before any weights are added with a millimetre ruler clamped to the stand
2. Take reading at eye level and add a marker at the bottom of the spring to make the reading more accurate
3. Add a mass to the spring and allow it to come to rest.
4. Record the mass and measure the new length of the spring (the extension is the change in length)
5. Repeat this process until you have at least 6 measurements
6. Plot a force extension graph it will only start to curve if you exceed the limit of proportionality but doesn’t matter if you don’t
If the line of best fit is a straight line it means there is a linear relationship between force and extension (they’re directly proportional) F=ke
K= gradient of the line
When the line begins to bend the relationship is now non linear
Work done for stretching can be found by doing #
Ee (J)= 1/2 k (N/m) x e² (m)
\
The energy in the elastic potential store is equal to the area under the force-extension graph
Test weights by using identical spring and see if the increase of extension after each weight is added stays the same up to at least 5 weights if it is you need to uses lighter weights or you won’t get enough measurements for your graph
1. Measure the natural length of the spring before any weights are added with a millimetre ruler clamped to the stand
2. Take reading at eye level and add a marker at the bottom of the spring to make the reading more accurate
3. Add a mass to the spring and allow it to come to rest.
4. Record the mass and measure the new length of the spring (the extension is the change in length)
5. Repeat this process until you have at least 6 measurements
6. Plot a force extension graph it will only start to curve if you exceed the limit of proportionality but doesn’t matter if you don’t
If the line of best fit is a straight line it means there is a linear relationship between force and extension (they’re directly proportional) F=ke
K= gradient of the line
When the line begins to bend the relationship is now non linear
Work done for stretching can be found by doing #
Ee (J)= 1/2 k (N/m) x e² (m)
\
The energy in the elastic potential store is equal to the area under the force-extension graph
19
New cards
Displacement
Distance moved + direction
20
New cards
Distance travelled equation
s=vt or distance travelled (m)= speed (m/s) x time (use mean speed if changing speed)
21
New cards
Speeds of different things
A person:
* walking- 1.5 m/s
* running- 3 m/s
* cycling - 6 m/s
\
Vehicles
* A car- 25 m/s
* A train- 30 m/s
* A plane- 250 m/s
* walking- 1.5 m/s
* running- 3 m/s
* cycling - 6 m/s
\
Vehicles
* A car- 25 m/s
* A train- 30 m/s
* A plane- 250 m/s
22
New cards
Acceleration
Change in velocity/time (s) or a=Δv/ t
23
New cards
Constant (Uniform) Acceleration
v² - u² = 2as or Final velocity (m/s) ² - Initial velocity (m/s) = 2 x Acceleration (m/s²) x Distance (m)
24
New cards
Distance-Time
If straight line stopped
gradient indicates speed
Curves indicate acceleration or deceleration
gradient indicates speed
Curves indicate acceleration or deceleration
25
New cards
Velocity time graphs
Gradient = acceleration
Flat - Steady speed no acceleration
Curved-increasing or decreasing acceleration
Uphill- acceleration
Downhill-Deceleration
Flat - Steady speed no acceleration
Curved-increasing or decreasing acceleration
Uphill- acceleration
Downhill-Deceleration
26
New cards
Friction
Slows down things if an object has no force propelling it along
Friction always acts in the opposite direction to movement
You get friction when two surfaces are in contact or when an object passes though a fluid (drag) .
You can reduce friction between surfaces with lubricants.
Friction always acts in the opposite direction to movement
You get friction when two surfaces are in contact or when an object passes though a fluid (drag) .
You can reduce friction between surfaces with lubricants.
27
New cards
Drag
\-Increases as speed increases
\-Drag is the resistance you get in fluid (a liquid or gas)
\-Air resistance is a type of drag
\-Streamlining the object is the most important factor in reducing drag
\-Streamlined-where an object is designed to allow fluid to flow easily across it , reducing drag. (parachutes work in the opposite way)
Frictional forces from fluids increase with speed. A car much more friction to work against when travelling at 70mph compared to 30. So at 70 mph the engine has to work harder
\-Drag is the resistance you get in fluid (a liquid or gas)
\-Air resistance is a type of drag
\-Streamlining the object is the most important factor in reducing drag
\-Streamlined-where an object is designed to allow fluid to flow easily across it , reducing drag. (parachutes work in the opposite way)
Frictional forces from fluids increase with speed. A car much more friction to work against when travelling at 70mph compared to 30. So at 70 mph the engine has to work harder
28
New cards
terminal velocity
When a falling object first sets off the force of gravity is much greater than frictional force slowing it down
As speed increases friction builds up
This gradually reduces the acceleration until eventually the frictional force is equal to the accelerating force (so the resultant force is zero)
It will have reached its maximum speed or terminal velocity and will fall at a steady speed
As speed increases friction builds up
This gradually reduces the acceleration until eventually the frictional force is equal to the accelerating force (so the resultant force is zero)
It will have reached its maximum speed or terminal velocity and will fall at a steady speed
29
New cards
Streamlining
\-depending on shape and area
\-the less streamlined an object is, the lower its terminal velocity
\-Objects with large surface areas tend to have lower terminal velocities.
\-e.g. if you dropped a marble off a roof it would have a higher terminal velocity than a beach ball as there is more air resistance acting on the beach ball. #
\-so the ball spends lest time accelerating before the air resistance is large enough to equal the accelerating force
\-the less streamlined an object is, the lower its terminal velocity
\-Objects with large surface areas tend to have lower terminal velocities.
\-e.g. if you dropped a marble off a roof it would have a higher terminal velocity than a beach ball as there is more air resistance acting on the beach ball. #
\-so the ball spends lest time accelerating before the air resistance is large enough to equal the accelerating force
30
New cards
Newton’s First Law
A resultant force is needed to make something start moving, speed up or slow down:
If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object zero, it’ll just carry on moving at the same velocity (same speed and direction)
Velocity will only change if there is a non zero resultant force which means it must be accelerating or decelerating.
If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object zero, it’ll just carry on moving at the same velocity (same speed and direction)
Velocity will only change if there is a non zero resultant force which means it must be accelerating or decelerating.
31
New cards
Newtons second law
Acceleration is proportional to resultant force
The larger the resultant force acting on an object acting on an object the more the object accelerates - they are directly proportional
Acceleration is also inversely proportional to the mass of the object
Force (N) = Mass (kg) x Acceleration (m/s²)
The larger the resultant force acting on an object acting on an object the more the object accelerates - they are directly proportional
Acceleration is also inversely proportional to the mass of the object
Force (N) = Mass (kg) x Acceleration (m/s²)
32
New cards
Required practical (extension)
Force and extension of a spring
Clamp stand
heavy weight on the stand
two clamps and bosses
attach metre rule and spring
Top of the spring must be at 0
bottom of spring has a pointer
add 1N weight to the spring and measure the extension
Plot extension against the weight
extension is directly proportional to the weight
A rubber band is non linear
the spring is elastic as the weight returns back to its original shape
If we add to much weight you can overstretch the spring and even after we have taken away the weights the spring would now still show an extension
this is called inelastic deformation
F=k x e
spring constant should be the same at all points before the limit of proportionality
Clamp stand
heavy weight on the stand
two clamps and bosses
attach metre rule and spring
Top of the spring must be at 0
bottom of spring has a pointer
add 1N weight to the spring and measure the extension
Plot extension against the weight
extension is directly proportional to the weight
A rubber band is non linear
the spring is elastic as the weight returns back to its original shape
If we add to much weight you can overstretch the spring and even after we have taken away the weights the spring would now still show an extension
this is called inelastic deformation
F=k x e
spring constant should be the same at all points before the limit of proportionality
33
New cards
Inertia
An object will stay still or keep the same motion unless you apply a resultant force.
34
New cards
Inertial mass
Measure of how difficult it is to change the velocity of an object. The ratio of force needed to accelerate an object over the acceleration produced
An object with a large inertial mass will require a larger force to produce a given acceleration than an object with a smaller inertial mass
An object with a large inertial mass will require a larger force to produce a given acceleration than an object with a smaller inertial mass
35
New cards
Newtons third law of motion
Whenever two objects interact, the forces they exert on each other are equal and opposite .
36
New cards
Required practical acceleration
trolley holding up a piece of card with a gap in the middle that will interrupt the signal of the light gate twice. Then measure both lengths of card so the computer can work out its acceleration.
Connect the trolley to a piece of string that goes over a pulley and is then connected on the other side to a hook( of known mass) which can have masses added to it
The weight of the hook and other masses attached provide the accelerating force
Make a starting line
Use the formula F=ma
Place the trolley on the starting line so the string is taut and release it
Record the acceleration measured by the light gate as acceleration of the whole system
Investigate the effect of mass by adding mass to the trolley
Investigate the effect of force by adding mass to the the hook, keeping the mass of the whole system the same
Connect the trolley to a piece of string that goes over a pulley and is then connected on the other side to a hook( of known mass) which can have masses added to it
The weight of the hook and other masses attached provide the accelerating force
Make a starting line
Use the formula F=ma
Place the trolley on the starting line so the string is taut and release it
Record the acceleration measured by the light gate as acceleration of the whole system
Investigate the effect of mass by adding mass to the trolley
Investigate the effect of force by adding mass to the the hook, keeping the mass of the whole system the same
37
New cards
Stopping distance
Total distance travelled from when the driver sees the obstruction to them coming to a stop
Thinking Distance + Braking distance
Thinking distance is the distance travelled by the car during the driver’s reaction time
Breaking distance how far car travels when breaks are applied
Stopping distance increases with speed
14m at 30 mph , 55m at 60 mph , 75m at 70 mph
Thinking Distance + Braking distance
Thinking distance is the distance travelled by the car during the driver’s reaction time
Breaking distance how far car travels when breaks are applied
Stopping distance increases with speed
14m at 30 mph , 55m at 60 mph , 75m at 70 mph
38
New cards
Reaction time
Ruler drop test
Acceleration due to gravity is 9.8 (m/s²) roughly
affected by tiredness, drugs or alcohol
Acceleration due to gravity is 9.8 (m/s²) roughly
affected by tiredness, drugs or alcohol
39
New cards
Forces and braking
Breaks convert kinetic energy into thermal energy due to the friction between the breaks and the wheel
This could cause the breaks to overheat and the driver may lose control
Force = mass x acceleration
30 m/s to 0 in 10 seconds
Losing 3 m/s² per second
This could cause the breaks to overheat and the driver may lose control
Force = mass x acceleration
30 m/s to 0 in 10 seconds
Losing 3 m/s² per second
40
New cards
Momentum
momentum is in all moving objects
non moving objects have no momentum
momentum= mass x velocity
(kg m/s) (kg) (m/s)
\
In a closed system the total momentum before an event is equal to the total momentum after the event
Momentum is conserved in a closed system
Recoil in a canon shooting a canon ball
non moving objects have no momentum
momentum= mass x velocity
(kg m/s) (kg) (m/s)
\
In a closed system the total momentum before an event is equal to the total momentum after the event
Momentum is conserved in a closed system
Recoil in a canon shooting a canon ball