Studied by 2 peopleDefine a ruler.
A ruler is used to measure length for distances from 1 millimeter to 1 metre.
State the formula to find the volume for a regular object.
width x height x length
Describe how to find the volume for an irregular object.
Measure by displacement : Put the object into a measuring cylinder with water. When the object added, it displaces water, making water level rise. Measure this rise. This is the volume.
What tools can be used to find large distances?
A trundle wheel Tape measure
What tools can be used to find mass?
A balance A scale
What tools can be used to find length?
A metre rule Tape measure Vernier calipers
What tools can be used to find volume?
A measuring cylinder Micrometer screw gauge
What tools can be used to find time?
A stop clock An electronic timer
Describe a micrometer screw gauge, and how to use it.
A micrometer screw gauge is used to find very small distances(less than a centimetre). It has two scales; the main scale and the rotating scale/ fractional scale. The units of the main scale is in millimetres (mm) and the fractional scale is 1/100th of the main scale, therefore it is 0.01mm
To measure: Thickness of object = main scale reading + fractional scale reading
What can be used to measure time intervals?
Stopclocks and stopwatches.
What is a significant factor to consider when measuring time?
Human reaction time.
What is the difference between an analogue clock and a digital clock?
In analogue clocks: Time is found by clock's hands A small wheel (the balance wheel) oscillates to and fro
In digital clocks: Gives direct reading of time in numerals The oscillations are produced by a tiny quartz crystal.
How would an accurate measure of the width of a single piece of paper be measured?
By taking multiple readings. Instead of trying to measure a single piece of paper, measure 100 and from that divide the measurement by the total number of pieces of paper. This is finding the average.
What tool would require multiple readings to be taken for an accurate measurement?
A pendulum
Define speed.
Speed is the distance moved by an object each second. It's units are metres per second (m/s)
State the formula of speed.
speed= distance/time s=d/t
Define velocity.
Velocity is a similar quantity to speed, but includes a direction. It is a vector quantity while speed is a scalar quanity. It is speed in a given direction.
Distance moved in a stated direction is called....?
Displacement
Define acceleration.
Acceleration is the rate of change of velocity: In other words, how much the velocity of an object changes by every second. It is a vector quantity. It's units are m/s^2
State the formula of acceleration.
acceleration = change in velocity/time taken a=(v-e)/t
An acceleration is ______________ if the velocity increases and negative if it ___________________. A negative acceleration is also called a _________________ or ____________________.
Positive Decreases Deceleration Retardation
In distance-time graphs: A horizontal line means __________________ A straight line means ___________ ___________ If the gradient _____________ the object is speeding up (accelerating) If the gradient ________________ the object is slowing down (decelerating) If the line is going down, the object is moving ______________
Stationary Constant speed Increases Decreases Backwards
State how to calculate speed in a distance-time graph.
The speed of an object is given by the gradient of the line. speed = gradient = rise/run
What are distance-time graphs also called?
Position-time graphs Displacement-time graphs
Define velocity-time graph.
A Velocity-time graph shows how the velocity (or speed) of an object changes over time.
If the line is _____________, the velocity is constant (no acceleration) If the line slopes upwards, then the object is ___________ If the line goes down then the object is ____________
Horizontal Accelerating Decelerating
State how to find distance moved in a velocity-time graph.
distance = area beneath the graph
(do NOT use the distance-speed-time equation)
What does the gradient of a velocity-time graph represent? How is it found?
Acceleration acceleration = gradient = rise/run (m/s^2)
Define the oscillation of a pendulum.
The number of swings/ period time
In the absence of _______________, all objects fall with the same ___________________, regardless of their mass
Air resistance Acceleration
State the gravitational field strength near the Earth's surface.
9.8 m/s^2 or 10 m/s^2 Units are also N/kg
The acceleration caused by the pull of the Earth's gravity is called the ____________________. This quantity is given the symbol __ and its value is 10m/s2 close to the surface of the _________.
Acceleration of freefall g Earth
Will the speed of a falling object change the longer it falls for?
Yes, it will increase.
Define terminal velocity.
The constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity
The force of gravity is called....?
Weight Gravitational attraction Gravitational Force
(do NOT refer to it as gravity/ gravitational field strength/ gravitational potential)
Define mass.
A measure of the amount of matter in an object. It is measured in kilograms, kg.
Define weight.
A measure of the force of gravity on an object. It is measured in Newtons, N. The size of this force depends on the gravitational field strength (often called gravity, g, for short)
State the formula for weight.
weight = mass * gravitational field strength
What factors is weight affected by?
Mass and acceleration. Therefore if there is motion, acceleration changes and so does weight but since mass is only affected by the amount of matter in an object, no matter what forces are acting on it, it will not change.
Define inertia.
Inertia: the resistance in change of velocity.
Describe the mass and weight for the same object on two different planets.
The mass is the same The gravitational field strength, g, on the two planets will be different, so the weight will be different.
The weight and mass of an object can be compared using a...?
Balance
State the two significant effects of mass in physics.
The mass of an object's opposed any attempt to change that object's motion The greater the mass of an object, the more difficult it is to speed it up, slow it down or change its direction. This property of mass is sometimes referred to as inertia
Mass is also the source of an object's weight - the force of gravity on a mass. The greater the mass, the greater the weight.
Define density and state its formula.
Density is the mass per unit volume of a material Its units are g/cm^3 or kg/m^3
density = mass/volume
An object will float in a liquid if the average density of that object is ______ than the density of the liquid it is placed in.
Less
Density of water?
1g/cm^3
State how to find the volume: Sphere Cylinder Cube
Sphere v=4/3 πr^3 Cylinder v=πr^2 * L Cube d^3
To find the volume of an irregular object, use a?
Eureka can or measuring cylinders and measure by displacement
Describe how forces may change the size, shape and motion of a body.
o Bending o Twisting o Compression o Extension
Define Hooke's Law.
The extension of a spring is proportional to the applied force(load), provided the limit of proportionality is not exceeded
State Hooke's Law Formula.
force = springs constant * extension
State Newton's first law of motion.
If no external force is acting on it, an object will, if stationary, remain stationary, and if moving, keep moving at a steady speed in the same straight line.
State Newton's second law of motion.
The change of motion of the body is proportional to the net force imposed on the body and is in the direction of the net force. F=ma
State Newton's third law of motion.
if object A exerts a force on object B, then object B will exert an equal but opposite force on object A
For every action, there is an equal and opposite reaction.
If there is no resultant force acting on an object(forces are balanced), an object will...?
Remain stationary/at rest Continue at a constant speed
Define friction.
A force that opposes motion between two surfaces that are touching. It always acts in the opposite direction to the direction in which the object is moving
Friction (including air resistance) results in energy _______ due to the transfer of energy from _________ to internal (heat)
Loss Kinetic
The resultant force is also known as...?
The net force or the unbalanced force.
When an unbalanced (resultant) force acts on an object, it can affect its motion by....?
The object could speed up The object could slow down The object could change direction
State the formula for force.
force = mass * acceleration f=ma
State how force, mass and acceleration are related.
The greater the mass of the object, the smaller the acceleration it is given by a particular force.
Describe qualitatively motion in a circular path due to a perpendicular force.
As the centripetal force acts upon an object moving in a circle at constant speed, the force always acts inward as the velocity of the object is directed tangent to the circle. This would mean that the force is always directed perpendicular to the direction that the object is being displaced.
The force needed to make something follow a circular path depends on a number of factors:
The mass of the object (a greater mass requires a greater force) The speed of the object (a faster-moving object requires a greater force) The radius of the circle (a smaller radius requires a greater force)
Define centripetal force and centrifugal force.
Centripetal force: the force that is acting towards the centre of a circle. It is a force that is needed, not caused, by circular motion.
Centrifugal force: the force acting away from the centre of a circle. The centrifugal force is the reaction to the centripetal force. It has the same magnitude but opposite direction to centripetal force.
Define moment and give an example involving it.
The turning effect of a force. Their units are N m, or N cm. e.g. opening/closing a door turning a tap on or off
The size of the moment depends upon:
The size of the force The distance between the force and the pivot
The moment of a force is greatest is if it acts 90° to the object it acts on
State the equation for moment of a force
moment of a force = force x distance to pivot
State the principle of moments.
For a system to be balanced, the sum of clockwise moments must be equal to the sum of anticlockwise moments clockwise moments = anticlockwise moments
State the conditions for equilibrium.
The forces on the object must be balanced (there must be no resultant force)
The sum of clockwise moments on the object must equal the sum of anticlockwise moments (the principle of moments)
Define the centre of mass/centre of gravity.
The point through which the weight of that object acts
Perform and describe an experiment to determine the position of the centre of mass of a plane lamina.
The irregular shape (a plane laminar) is suspended from a pivot and allowed to settle A plumb line (lead weight) is then held next to the pivot and a pencil is used to draw a vertical line from the pivot (the centre of mass must be somewhere on this line) The process is then repeated, suspending the shape from two different points The centre of mass is located at the point where all three lines cross
Describe qualitatively the effect of the position of the centre of mass on the stability of simple objects
If the centre of mass is below the point of suspension of an object, it will be in stable equilibrium (e.g., a hanging pot). If the centre of mass is above the point of suspension of an object, it will be in unstable equilibrium (e.g., a pencil placed on the sharp end). If the line of action of the object's weight moves outside the base, there will be a resultant moment and it will topple.
Stable objects have...?
The most stable objects have a low centre of mass and a wide base
Define scalar and vector quanities.
Scalars are quantities that have only a magnitude Vectors have both magnitude and direction
State common scalars and vectors
Describe how the resultant vector can be found graphically(vector addition).
o Draw arrows end-to-end, so that the end of one is the start of the next. o Choose a scale that gives a large triangle. o Join the start of the first arrow to the end of the last arrow to find the resultant.
Tip to tip can also be used, that would form a parallelogram.
Define and state the formula of momentum.
momentum = mass × velocity p = m × v Momentum is defined as the product of mass and velocity. Its units are kg m/s. It is a vector quanity, meaning it can be negative as well as postive.
State principle of the conservation of momentum.
In the absence of external forces (such as friction), the total momentum of a system remains the same. total momentum before = total momentum after
Define and state the formula for impulse.
impulse = change in momentum F × t = mv - mu or ft = m(v-u) impulse = force × time impulse = F × t
Define energy.
Energy is the capacity of something to do work
State the law of conservation of energy.
Energy cannot be created or destroyed, it can only transferred from one place to another.
List the types of energy.
Kinetic Gravitational potential Chemical Elastic (strain) Nuclear Internal energy
State the four ways in which energy can be transferred from one form to another.
Forces (mechanical working) Electrical currents (electrical working) Heating - by conduction, convection and thermal radiation Waves - light and sound carry energy
When energy is transferred from one form to another, not all of the energy will end up in the desired form. This lost energy often ends up being dissipated (spreading out into the environment). What is the form of this lost energy?
Heat, sound and light.
Define gravitational potential energy. State the formula of g.p.e.
Energy an object possesses because of its height in a gravitational field.
gravitational potetntial energy = mass x gravitational field strength x height GPE=mgh
Define kinetic energy. State its equation.
The kinetic energy (KE) of an object is the energy it has as a result of its speed. Kinetic energy = 1/2 x mass x speed^2
State the energy resources and their energy forms.
Fuels - chemical Water - gpe Waves - ke Geothermal - internal Nuclear fission - nuclear Solar heating - light Solar cells - light Wing - ke
What factors should be considered when giving the pros and cons of energy resources?
Reliability Environmental impact Cost Scale Renewability
Two advantages of all non-renewable fuels are...?
o their high energy density (i.e. they are concentrated sources) and the relatively small size of the energy transfer device (e.g. a furnace) which releases their energy o their ready availability when energy demand increases suddenly or fluctuates seasonally.
The Sun is the source of all energy except...?
Geothermal Nuclear Tidal
The Sun's energy is produced through nuclear fusion. Define nuclear fusion.
Nuclear fusion involves the collision (and bonding) of hydrogen nuclei to form helium nuclei, releasing nuclear energy in the process
The efficiency of a system can be increased by:
o Reducing waste output (lubrication, thermal insulation etc) o Recycling waste output (e.g., absorbing thermal waste and recycling it as input energy)
Define efficiency.
Efficiency is a measure of how much useful work is done with the energy supplied.
State the equation for efficiency.
Efficiency = useful energy output ÷ total energy input Efficiency = useful power output ÷ total power input
Define work done and state its formula.
Work is done whenever a force acts on an object that moves (or is moving) in the direction of the force
energy transferred (J) = work done (J)
work done = force × distance moved W = F× d
Its units are joules(J) or Nm
Define power and state its formula.
Because work done is equal to energy transferred, the power is also equal to the rate of doing work. Power is the amount of energy transferred (rate of work done) every second. power = energy transferred(work done)/ time The unit of power is the Watt (W), or Joules per second (J/s)
Define pressure and state its formula.
Pressure is the concentration of a force. pressure = force/area p = f/a Its units are N/cm^2, N/m^2 or Pascals (Pa) 1 Pa is the same as 1 N/m^2
The pressure in a liquid when an object is immersed in it depends upon a couple of factors:
The depth of the liquid The density of the liquid
The bigger either of these factors, the greater the pressure
Formula for pressure in liquids.
pressure = depth x density x gravitational field strength P = hρg
Describe the simple mercury barometer and its use in measuring atmospheric pressure.
A barometer is a device that is used to measure air pressure. A simple barometer consists of a column of mercury in an inverted tube, sat in a tray of mercury exposed to the atmosphere. The weight of the mercury in the tube is balanced by atmospheric pressure pushing down on the mercury in the tray. If atmospheric pressure increases, a greater length of mercury can be supported in the tube. If atmospheric pressure decreases, then less mercury will be supported in the tube.
Note
Flashcard