Forces

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3º de ESO Física (Topic 5: Forces) Flashcards on Forces, created by Carmen Diaz on 15/10/2018.
Carmen Diaz
Flashcards by Carmen Diaz, updated more than 1 year ago
Carmen Diaz
Created by Carmen Diaz about 6 years ago
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Resource summary

Question Answer
What's a force? A force is a push or a pull on an object that is caused by it interacting with something
What's a vector quantity? Vector quantities have a magnitude and a direction
Examples of vector quantities? -Force -Velocity -Displacement -Acceleration -Momentum
What's a scalar quantity? Scalar quantities only have a magnitude and don't have a direction
Examples of scalar quantities? -Speed -Distance -Mass -Temperature -Time -Energy
What are the two types of forces? -Contact forces -Non-contact forces
What's a contact force? A contact force is when two objects have to be touching for the force to act
Examples of contact forces? -Friction -Air resistance -Tension in rope -Normal contact force
What's a non-contact force? A non-contact force is when two objects don't need to be touching for the force to act
Examples of non-contact forces? -Magnetic force -Gravitational force -Electrostatic force -Nuclear force
What's an interaction pair? An interaction pair is a pair of forces that are equal and opposite and act on two interacting objects. (NEWTON'S THIRD LAW)
What's gravitational force? Gravitational force is the force of attraction between masses
Two important effects of gravitational force -On the surface of a planet, it makes all things fall towards the ground -It gives everything weight
What's the gravitational field strength in Earth? The gravitational field strength in Earth is 9.81
How does the gravitational field strength vary with location? The gravitational field strength it's stronger the closer you are to the mass causing the field (for example Earth), and stronger for larger masses
What's mass? Mass is just the amount of 'stuff' in an object. For any object it's mass will be the same value
Is mass a force? Mass is not a force
What's mass measured? Mass is measured in kilograms (kg) with a mass balance
What's weight? Weight is the force acting on an object due to gravity (the pull of the gravitational force on the object)
What does weight depend on? Weight depends on the strength of the gravitational field at the location of an object. This means that the weight of an object changes with its location
What's weight measured? Weight is measured in newtons (N) using a calibrated spring balance
Formula for weight WEIGHT (N) = MASS (kg) * GRAVITATIONAL FIELD STRENGTH (N/kg)
Differences between weight & mass -Weight is a force, mass isn't -Mass always stays the same, weight changes depending of the location of the object
Is mass & weight directly proportional to each other? Yes, mass & weight are directly proportional. As increasing the mass of an object increases it's weight. Weight & mass are directly proportional because if you double the mass the weight doubles too.
What's a resultant force? Resultant force is a single force that has the same effect as all the original forces together
What does the resultant force do? The resultant force moves an object through a distance, so energy is transferred and work is done on the object
Formula for resultant force RESULTANT FORCE (N) = MASS (kg) * ACCELERATION (m/s2)
When is work done? Work is done only when a force is applied on an objects and causes the object to move in the same direction as the force
Consequences moving a object? The thing applying the force needs a source of energy (like fuel ir food), so the resultant force does 'work' and moves the object and energy is transferred from one store to another. (Work done and energy transferred are the same thing)
Formula for work done WORK DONE (J) = FORCE (N) * DISTANCE (m)
What's the centripetal force? The centripetal force is the force towards the center of the circle
What does centripetal force create? -Changing direction -Acceleration -Velocity
Important equation of motion FINAL VELOCITY (m/s) = INITIAL VELOCITY (m/s) + TIME (s) + 1/2 * ACCELERATION (ms-2) * (TIME (s))2
Distance-time graphs shape - Gradient = speed (The steeper the graph, the faster the object is going) -Flat sections are where the object's stationary, it's stopped -Straight uphill sections mean it is traveling at a steady speed -Curves represent acceleration or deceleration -A steepening curve means the object's speeding up (increasing gradient) -A leveling off curve means it's slowing down (decreasing gradient)
Formula for gradient in distance-time graphs GRADIENT = CHANGE IN DISTANCE (m) / CHANGE IN TIME (s) = VELOCITY
Velocity-time graphs shape -Gradient = acceleration, as acceleration is change in velocity / time -Flat sections represent traveling at a steady speed - The steeper the graph, the greater the acceleration or deceleration -Uphill sections are acceleration. Downhill sections are deceleration. A curve means changing acceleration
Formula for gradient in velocity-time graphs GRADIENT = CHANGE IN VELOCITY (m/s) / CHANGE IN TIME (s) = ACCELERATION (m/s/s)
What's hooks law? ...?
What's Newton's first law? Newton's first law is that an object in equilibrium will continue in it's current state of motion unless acted upon by an external force
What's Newton's second law? Newton's second law is that the acceleration of an object i proportional to the resultant force that is producing it. Force is directly proportional to acceleration
Formula for Newton's second law FORCE (N) = MASS (kg) * ACCELERATION (m/s/s)
What's Newton's third law? Newton's third law is when two objects interact, the forces they exert on each other are equal and opposite
What's inertia? Inertia is the tendency for motion to remain unchanged (to continue in the same state of motion)
How do you make an object stretch, compress or bend? To stretch, compress or bend an object yo need more than one force acting on the object. Otherwise the object would simply move in the direction of the applied force, instead of changing shape
What is work done transferred to? Work done when an object stretches or compresses, the energy is transferred to elastic potential energy store of the object
What's elastic deformation? Elastically deformed is when an object can go back to its original shape and length after the force has been removed
What are elastic objects? Elastic objects are objects that can be elastically deformed
What's inelastic deformation? Inelastically deformed is when an object doesn't return to its original shape and length after the force has been removed
Formula for extension of a spring FORCE (N) = SPRING CONSTANT (N/m) * EXTENSION (m)
Is the extension of the spring directly proportional to the force? Yes, the extension of the spring is directly proportional to the force
What's the limit of proportionally? The limit of proportionally is the limit to the amount of force you can apply to an object for the extension to keep on increasing proportionally. There is a maximum force above which the graph curves, showing that the extension is no longer proportional to force
What's a moment? A momento is the turning effect of a force
How do you make an object to rotate? An object to rotate is caused by a force or several forces
Formula for moment MOMENT (Nm) = FORCE (N) * DISTANCE (m)
What's pressure? Pressure is the force per unit area
What are fluids? Fluids are substances that can 'flow' because their particles are able to move around
What does a pressure of a fluid mean? The pressure of a fluid means a force is exerted normal (at right angles) to any surface in contact with the fluid
Formula for pressure PRESSURE (Pa) = FORCE (N) / AREA OF THAT SURFACE (m2)
What does pressure in a liquid depend on? It depends on depth and density
What's density? Density is a measure of the 'compactness' of a substance (how close together the particles in a substance are)
How does the density in a liquid or gas vary? -In a liquid the density is uniform (the same everywhere) and it doesn't vary with shape or size -The density of a gas can vary
Formula for pressure at a certain depth PRESSURE (Pa) = HEIGHT OF THE COLUMN OF LIQUID [THE DEPTH] (M) * DENSITY OF THE LIQUID (kg/m3) * GRAVITATIONAL FIELD STRENGTH (N/kg)
What's upthrust? Upthrust is a force that determines whether an object will sink or float
When does an object float? An object floats if the upthrust in an object is equal to the object's weight, so the forces are balance and the object floats
When does an object sink? An object sinks if the object's weight is more than the upthrust, so the object sinks
What's distance? Distance is how dar an object has moved (it's a scalar quantity, as it doesn't have a direction)
What's displacement? Displacement measures the distance and direction in a straight line from an object's starting point to its finishing point (it's a vector quantity)
What's speed? Speed is just how far you're going with no regard to the direction (it's a scalar quantity)
What's velocity? Velocity is speed in a given direction (it's a vector quantity)
Formula for distance travelled DISTANCE TRAVELLED (m) = SPEED (m/s) * TIME (s)
Typical speeds -A person walking: 1.5 m/s -A person running: 3 m/s -A person cycling: 6 m/s -A car: 25 m/s -A train: 55 m/s A plane: 250 m/s
What can wind speed be affected by? Wind speed can be affected by: -Temperature -Atmospheric pressure -Large buildings or structures nearby
What's acceleration? Acceleration is the rate of change of velocity (how quickly you're speeding up)
What's deceleration? Deceleration is just negative acceleration (when something slows down, the change of velocity is negative)
Formula for acceleration ACCELERATION (m/s/s) = CHANGE IN VELOCITY (m/s) / TIME (s)
What's uniform acceleration? Uniform acceleration means a constant acceleration
Formula for uniform acceleration (FINAL VELOCITY)2 (m/s) - (INITIAL VELOCITY)2 (m/s) = 2 * ACCELERATION (m/s/s) * DISTANCE (m)
What's drag? Drag is the resistance you get in a fluid (a gas or a liquid)
What's air resistance? Air resistance is a type of drag. It's the frictional force produced by the air acting on a moving object
Important factor for reducing drag? The mast important factor in reducing drag is keeping the shape of the object streamlined. This is where the object is designed to allow fluid to flow easily across it, reducing drag
Steps of objects falling through fluids -When falling objects first set off, the force of gravity is much more than the frictional force slowing them down, so they accelerate -As the speed increases the friction builds up -This gradually reduces the acceleration until eventually the frictional force is equal to the acceleration force (so the resultant force is zero) -It will have reached its maximum speed or terminal velocity and will fall at a steady speed
What does terminal velocity depend on? Terminal velocity depends on: -Shape -Area
What's gravity? Gravity is the accelerating force acting on all falling objects and it will make them all fall at the same rate, if it wasn't for air resistance
What is terminal velocity of any object determined with? The terminal velocity of any object is determined by its drag in comparison to its weight
What does frictional force depend on? Frictional force depends on: -Shape -Area
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