# Forces:Topic 5

• Created by: Lahlah_8
• Created on: 24-11-18 12:05
• Forces:Topic 5
• Force Basics: 5a
• Contact Forces
• Non-Contact Forces
• Contact
• When two objects have to be touching for the force to act
• Examples: Friction, Air Resistance, Tension in ropes, Normal contact forces.
• Non-Contact
• When two objects do not need to be touching order for the force to be acting
• Examples: Magnetic forces, Gravitational forces, Electrostatic forces.
• Vector
• A quantity with both Direction and Magnitude
• Examples: Force,Velocity, Displacement, Acceleration, Momentum
• Scalar
• A Scalar quantity is one with Magnitude and no Direction
• Examples: Speed, Distance,Mass, Temperature, Time
• Weight
• Mass
• Gravity
• Makes all things accelerate towards ground.
• It gives everything weight.
• Effects:
• Amountof matter in an object
• The force acting on an object due to gravity.
• Measured with a Newtonmeter
• Resultant Forces
• With a numberof forces acting at a single point, replace them with a single force
• Resolving Forces
• Balanced forces
• Tip to tail
• Work Done
• When a force moves an object throughdistance, energy is transferred and work Is done on the object.
• WORK DONE(J) = DISTANCE (M) X FORCE(N)
• Working against a frictional force
• WORK DONE(J) = DISTANCE (M) X FORCE(N)
• Gravity,Mass and Weight
• Weight
• Mass
• Gravity
• Makes all things accelerate towards ground.
• It gives everything weight.
• Effects:
• Amountof matter in an object
• The force acting on an object due to gravity.
• Measured with a Newtonmeter
• WEIGHT (N) = MASS (KG) X GRAV. FIELD STRENGHT (N/KG)
• Forces and Elasticity: 5b
• Elastic Objects
• Elastically deformed
• Can go back to original shape an length once force Is removed
• Inelastically deformed
• Cannot return to original length or shape after force is removed
• FORCE(N) = SPRING CONSTANT (N/M) X EXTENSION (M)
• Extension is DirectlyProportional to load of force applied
• Limit of Proportionality
• The limit to the amount of force you can apply to an object for the extension to keep increasing proportionally
• Force- extension graph = curves upwards
• Extension-force graph = Curves downwards
• Investigating Springs
• ELASTIC POTENTIAL (J) = 1/2 X SPRING CONSTANT (N/M) X EXTENSION (M)2
• Equipment: Spring, clamp, fixed ruler, pointer,hanging mass, masses, weight stand
• Use W=mg
• Record at eye level and repeat experiment avoiding any human error (although Random error will occur)
• Force/ Extension graph =  line with slight curve
• Changes y/ Changein x = F/E = K
• Calculating speed
• Forces and Motion: 5c
• Accelertion
• How quickly the velocityis changing
• ACCELERATION(M/S2)= CHANGE IN VELOCITY(M/S) / TIME TAKEN(S)
• Uniform acceleration
• Uniform acceleration is constant acceleration
• FINAL VELOCITY 2 (M/S) - INITIAL VELOCITY (M/S) = 2 X ACCELERATION(M/S2) X DISTANCE (M)
• Distance-Time Graphs
• Motion of something travelling in a straight-line
• Steeper= faster
• levelling off = decreasing in speed
• curves represent acceleration
• SPEED= DISTANCE / TIME
• Calculating speed
• Terminal velocity
• Friction
• If an object has no force propelling it then friction will slow it down
• always acts in opositedirection
• you get friction between two surfaces or an object passingthrougha fluid
• Drag
• most resistive forces = air resistance or drag
• keep object streamlined to reduce any drag = flow over more easily
• Increasing top speed
• reducing drag = streamined
• Increasing power o engine = driving force increases and drag force becomes equal to it
• Velocity-time graphs
• Shows objectsotion
• curve= changing acceleration
• downhill = deceleration
• Distance traveled
• change in vertical / changes horizontal
• AREA = BASE X HEIGHT
• Newton'sFirst Law
• Newton'sSecond Law
• Newton'sThird Law
• when two objects interact, the forces they exert on each other are equal and opposite
• Equilibrium
• State which forces are equal and opposite
• RESULTANT FORCE(N) = MASS(KG) X ACCELERATION (M/S2)
• if the resultant force on a stationary object is zero, the object remains stationary
• if resultant force on a moving object is zero, it will carry on at the same velocity
• if there is a non-zero resultant force on an object, its velocity will change(accelerate in the direction of force)
• Inertia
• INERTIAL MASS (KG) = RESULTANT FORCE(N) / ACCELERATION (M/S2)
• Distance, Displacement, Speed and velocity
• Displacement
• Displacement is the distance and direction in a straight-line from n objectsstartingto finish point.
• Distance
• Distance is how far an object has moved
• Speed
• How fast something is going, no regardsdirection
• Velocity
• How fast something is going and in what direction
• Everyday speeds
• Walking= 1.5m/s
• Running = 3m/s
• Cyling = 6m/s
• Car = 25m/s
• Train = 55m/s
• Plane = 250m/s
• Investigating Motion
• Equipment: trolley, hook with mass, masses, pulley and light gate connected to data logger
• Car Safety and Momentum: 5d
• Stopping Distnace
• STOPPING DISTANCE = THINKING DISTANCE + BRAKING DISTANCE
• Thinking distance
• distance the vehicle travels during drivers reaction time
• Brakingdistance
• Stopping Distnace
• STOPPING DISTANCE = THINKING DISTANCE + BRAKING DISTANCE
• Thinking distance
• distance the vehicle travels during drivers reaction time
• Brakingdistance
• distance the vehicle travels after braking
• how fast, quality of brakes, tyres, road surface, good grip
• How fast, how quick
• Typical stopping distances
• 30mph = 9m Think + 14m Brake
• 50mph = 15m Think +38m Brake
• 70mph = 21m Think + 75m Brake
• distance the vehicle travels after braking
• how fast, quality of brakes, tyres, road surface, good grip
• How fast, how quick
• Typical stopping distances
• 30mph = 9m Think + 14m Brake
• 50mph = 15m Think +38m Brake
• 70mph = 21m Think + 75m Brake
• Reaction Time
• Ruler-drop test
• Braking
• Brakingrelies on frictiion from brakes and wheels
• Frictioncauses work to be done
• Estimate:
• Rearrange V2-U2 = 2as
• Energy Transfer
• Momentum
• MOMENTUM (KGM/S) = MASS(KG) X VELOCITY(M/S)
• Greatermass = greater velocity= more momentum
• Conservation of Momentum
• In a closed system the overall momentum is the same before as it is after