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Description
Flashcards by Jessie Howes, updated more than 1 year ago
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Created by Jessie Howes
over 6 years ago
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| Question | Answer |
| What is a vector quantity? | A vector quantity has a magnitude and a direction |
| Give 3 examples of vector quantities | Force Velocity Displacement Acceleration Momentum |
| What's a scalar quantity | A scalar quantity has a magnitude but no direction |
| Name 3 examples of scalar quantities | Speed Distance Mass Temperature Time |
| How are vectors usually represented? | With arrows- the size represents magnitude and the direction of the arrow shows the direction of the quantity |
| What's a force? | A push or pull on an object caused by interacting with something |
| What's a contact force? | When two objects have to be touching in order for a force to act |
| Give 3 examples of contact force | Friction Air Resistance Tension in ropes Normal Contact force |
| What's a non contact force | When the objects don't have to be touching for the force to act |
| Give 3 examples of non contact force | Magnetic Force Gravitational Force Electrostatic Force |
| What's an interaction pair? | A pair of forces that are equal and opposite and act on two interacting objects. i.e a chair pushes on the ground (gravity), but the ground pushes on the chair (supporting) |
| What is gravitational force? | The force of attraction between masses (happens with all masses, but only noticeable when one is really big - like a planet) |
| What are the two important effects of gravity? | 1. All things fall towards the ground on the surface of a planet 2.Gives everything a weight |
| What is mass? | The amount of 'stuff' in an object. It doesn't change depending on the strength of gravity |
| What is weight? | The force acting on an object due to gravity (the pull of the gravitational force on an object) |
| What does the gravitational field strength vary on? | Location- the closer you are, the stronger it is, meaning weight changes with location |
| What is weight measured in? | Newtons (N) |
| What is the centre of mass? | The point where the force acts from (it will be at the centre of a uniform object) |
| How is weight measured? | With a calibrated spring balance or a newtonmeter |
| What is the equation for weight? | Weight (N) = mass (kg) x Gravitational Field Strength (N/kg) |
| True or false: Weight is indirectly proportional to weight | False - they're directly proportional |
| What does a free body diagram show | The forces acting on an object, but not the forces the object is exerting on the rest of the world |
| What do the arrow sizes in a free body diagram represent? | The magnitude and direction of the force acting on the object |
| What's a resultant force? | The total force acting on an object (i.e a skydiver with an upward force of 2N and a downwards force of 10N would have a resultant force of 8N accelerating downwards) |
| What happens when a force moves an object through a distance? | Energy is transferred and work is done |
| What energy types are being transferred when a object is being dragged along a carpet (frictional force) | Object moving - some transferred to kinetic energy stores Friction - some transferred to thermal energy stores, so object heats up |
| Whats the equation for finding out how much work has been done? | Work done (J) = Force (N) x distance (m) |
| How do you convert Joules into Newtonmeters? | 1J=1Nm One Joule of work is done when a force of one newton moves an object a distance of one meter. |
| How do you use a scale drawing to find the total resultant force? | 1. Draw the vertical and horizontal forces at a 90 degree angle using a sensible scale 2.Draw a line from the ends of the two forces, forming a right angle triangle 3. Measure the length and use the scale to find the force 4. Use a protractor to measure the direction as a bearing |
| What's the resultant force of an object in equilibrium? | 0N |
| What does a scale drawing of an object in equilibrium look like? | All of the force lines join together - no need for a resultant force line |
| How do you resolve a force (split it into components)? | Draw the force line to scale, then draw the horizontal and vertical components from the end of the line, which you can just measure. |
| What does elastically deformed mean? | The object returns to its original shape after being stretched/ bent/ compressed |
| What does being inelastically deformed mean? | Doesn't return to it's original shape after being compressed/stretched/bent |
| Where does energy transfer to when an object changes shape? | Elastic potential energy store |
| Extension is directly proportional to what? | Force |
| What's the equation of the force acting on a spring while being stretched? | Force (N) = Spring constant (N/m) x Extension (m) |
| What does the spring constant depend on? | The material being stretched - the stiffer the spring, the greater the spring constant |
| What's the equation for the force acting on a spring while being compressed? | Force (N) = Spring constant (N/m) x difference between natural and compressed lengths (m) |
| What's the limit of proportionality? | The point where extension is no longer directly proportional to force |
| What's the equation for the work done in stretching/compressing a spring? | Elastic Potential Energy (J) = 1/2 x Spring constant (N/m) x extention^2 (m) |
| How do you find the spring constant from an extension-force graph? | It's equal to the gradient of the line |
| What's a moment of a force? | The turning point (object rotates) |
| What's the equation for a moment of a force? | Moment of a force (Nm) = Force (N) x distance (m) Distance = perpendicular distance from pivot to line of action of the force |
| Why won't a balanced object rotate? | the anticlockwise moment = the clockwise moment You can use this to calculate a missing force or distance |
| Why do levers make it easier to do work? | Increases the distance from the pivot. M=Fd, so less force is needed to get the same moment |
| What do gears do? | Transmit rotational effect of a force from one place to another |
| What do different sized gears change? | The moment of the force - a larger gear has a greater moment as there's a bigger distance from the pivot |
| What is pressure? | The force per unit area |
| What is the pressure of a fluid? | The force exerted at right angles to any surface in contact with the fluid |
| What's the equation for pressure? | Pressure (Pa) = Force (N) / Area of surface (m^2) |
| Why is pressure higher when a liquid is more dense? | There's more particles to exert a force on the surfaces in contact with the liquid. |
| What's the equation for calculating pressure at a certain depth? | Pressure (Pa)= Depth (m) x density (kg/m^3) x gravitational field strength (Normally write answer in standard form) |
| Why do objects in fluids experience upthrust? | When an object in in fluid, the pressure of the fluid exerts a force in every direction. Pressure increases with depth, so there's more force acting on the bottom of the object than the top Therefore there's an upward resultant force called upthrust. |
| What is upthrust equal to? | The weight of the fluid that has been displaced by the object |
| Why do objects float? | When the upthrust on an object is equal to the object's weight, the force balances and the object floats |
| When does an object sink? | When the object's weight is more than the upthrust |
| Explain how density links to whether an object will float or sink | An object that's less dense than the liquid weighs less than the equivalent volume of fluid. It displaces a volume of weight equal to it's weight before it's fully submerged An object that's more dense than the fluid is unable to displace enough fluid to equal it's weight so it sinks, as the weight is larger than the upthrust |
| Why does atmospheric pressure decrease when altitude increases? | Atmosphere is less dense - there're fewer air molecules to collide with the surface. Also, there are less air molecules above the surface so the weight of the air above decreases with altitude |
| What is distance? | How far an object moves |
| What is displacement? | Measures distance and direction in a straight line from the starting point to the finishing point. Direction could be relative to a point (i.e. towards the building) or as a bearing |
| What is speed? | A measure of how fast an object is going |
| What is velocity? | A measure of how fast an object is going in a given direction (30 mph north or as a bearing) |
| How can an object have a constant speed but a changing velocity? | It changes direction while staying at the same speed |
| Whats the equation for speed? | Speed = Velocity x Time |
| What's the equation for distance travelled | Distance = Speed (m/s) x time (s) |
| What's the average speed of a person walking? | 1.5 m/s |
| What's the average speed of a person running? | 3 m/s |
| What's the average speed of a person cycling? | 6 m/s |
| What's the typical speed for a car? | 25 m/s |
| What's the typical speed of a train? | 55 m/s |
| What's the typical speed of a plane? | 250 m/s |
| What are 3 factors effecting the speed at which a person can walk, run or cycle? | Age Fitness Distance Traveled Terrain |
| Name 3 factors affecting wind speed | Temperature Atmospheric Pressure Large Structures and buildings nearby |
| What is acceleration? | How quickly an object is speeding up |
| What's the formula for finding an average acceleration? | Acceleration (m/s^2) = Change in velocity (m/s) / time (s) |
| What is deceleration? | How quickly an object slows down - it has a negative change in velocity, and the average acceleration will be a negative value |
| EXAM QUESTION NOTE | The exam board could ask for acceleration, but using estimates, so they don't give you any values |
| What is uniform acceleration? | Constant acceleration - accelerating at a constant rate |
| What's the equation for finding uniform acceleration? | Final Velocity^2 (m/s) - Initial velocity^2 (m/s) = 2 x acceleration (m/s^2) x distance (m) |
| How do you calculate speed from a distance time graph? | Speed = Gradient (Distance/ Time) |
| How do you find the acceleration from a velocity time graph? | Acceleration = Gradient |
| Why will a moving object with no force propelling it, slow down or stop? | Friction |
| How does friction act upon an object? | In the opposite direction to movement |
| What needs to happen in order to travel at a constant speed? | The driving force needs to be balanced with the frictional forces |
| When do you get friction? | Two surfaces in contact Passing through a fluid (drag) |
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