IGCSE-physics- Mechanics
Explain the difference between renewable and non-renewable energy resources.
Renewable energy resources are energy derived from resources that will be constantly replenished and not become in limited supply. They will be replensihed within your lifetime. Non-renewable energy resourfces drvie energy from sources where they are not constantly replenished. These are not replaced in one's lifetime.
Define the resultant force in terms of momentum? State the equation.
Resultant force is the rate of the change of momentum. F= (mv-mu)÷t
what are SI units? Name five SI units.
SI units (Le Système international d'unités) is a complete metric system of units, adopted for international use and measurement in science. e.g. meter, secound, ampere, mole, kelvin etc.
What is the difference between precision, accuracy and uncertainty
Precision is how many significant digits a value is measured at, or how close the values are in relation to each other. (the repeatability of the results) Accuracy is how close a measurement is to the "actual" value. Uncertainty of a measured value is an interval around that value such that any repetition of the measurement will produce a new result that lies within this interval.
What is a force? And what does it cause?
A force is any influence (a push, pull or twist) that may produce a change in shape and size of a freebody. Forces causes a free body to undergo an acceleration.
What are Base units? Name the seven Base units
A fundamental unit that is defined arbitrarily and not derived by combinations of other units. the seven base units are metre, kilogram,secound, ampere, kelvin, candela and mole
Describe how hydroelecticity works.
A large resevoir of water is stored behind the dam. Valves in the dam are opend, this allows water to through the dam into the river below. The flow of water through these valves turen turbines and drive a dynamo which generates electricity. Gravitational potential energy→kinetic energy→kinetic energy→electrical energy.
What is a moment? How do you calculate a moment?
A moment is the turning effect of a force. It is measured in Newton meters (Nm.) Moment(Nm)= Force(N)x Prependicular distance from the pivot(m.)
What is the gradient on a force-extension graph equal to?
The stiffness constant (lol) or the spring constant (if its a spring)
Explain what is meant by inertia
The tendency of a body to maintain its state of rest or uniform motion unless acted upon by an external force. Inertias is porportional to mass.
What happens if a elastic material is pulled past the elastic limit?
the material will behave PLASTICLY. where there is no link between the extension and the restoring force. When the force is taken away, permenant deformation occurs.
How do you calculate weight
weight (N) = mass (m) × gravitational field strength/ acceleration (Nkg⁻¹) gravitational acceleration on earth is ≈ 9.81 ms⁻²
Discuss the advantages and disadvantages of renewable and non renewable resources
1. For renewable resources a.) Constantly replenised, dosent contribte to global warming and has a low running cost. b.) They have high installation costs and have periodical energy production. 2. For Non-renewable resources a.) Fuel readily avalib (For now...) and fuel has a high energy density. There is a continuous energy output. b.) Contributes towards pollution, acid rain and global warming. These resources are finite, thus, will run out eventually
Describe freefall parachuting, with reference to unbalanced forves acceleration and terminal velocity.(Part 1.)
1. Jump out of the plane - there is a single point where there is no resistance, then as you fall downwards you start to accelerate downwards. 2. After falling for a few secounds - as your velocity increases due to your acceleration downwards, the air resistance increases ∴ your rate of acceleration starts to decrease. 3. After falling for about a minute - when air resistance and uplift are equal but opposite to your acceleration, there is no acceleration due to the forces being balanced. You reach a constant velocity called terminal velocity.
Describe an experiment to find the center of mass for a irregular lamina.
1.) Use a pin to suspend freely the lamina and the plumbline together. Trace the plumbline nto the lamina using a pencil. 2.) Rotate the lamina and place the pin on another side of the lamina. Repeat step one. 3.) Where the two traced pencil lines meet is where the center of mass is.
what does the gradient on a distance-time graph represent?
speed (ms⁻¹)
How do you find the displacement from a velocity-time graph?
+ve area − -ve area
Why do motorcyclists bend over when doing turns?
...
Describe freefall parachuting, with reference to unbalanced forces acceleration and terminal velocity.(Answers Continued.
4. Just opened parachute - air resistance shoots up but gravitational acceleration is always constant ∴ forces are unbalanced and rapid deceleration downwards occurs. 5. 15 secounds after opening parachute - as your velocity decreases the air resistance also decreases, so the rate of deceleration downwards decreases 6. 30 secounds after opening parachute - air resistance combined with uplift is now equal but opposite to the weight force. You reach a slower terminal velocity. 7. touch down - your weight downwards is equal but opposite to the upwards the force the earth is pushing at you (called the reaction force)
Explain what is meant by acceleration and how we would calculate it.
Acceleration is the rate of, the change of speed. Calculated by: a = (v − u) ÷ t
Why is the acceleration of an object in cirlular motion said to be changing when its speed is constant.
Acceleration means either speed or direction is changing, even thuo the speed of the object is constant, its direction (∴ its velocity) is changing.
State Newton's 1st law
An object remains motionless or at constant velocityas long as the forces acting on it are balanced (∑=0)
Define a Fuel
An store of energy that has economical and practical benefits for releasing the energy.
In the abscence of air resistance, what happens if you were pushed off a plane in the earth's atmosphere.
Anybody falling freely under the earths gravitation field will fall with a CONSTANT acceleration of around 9.81 ms⁻². Also all bodies regardless of mass, density, temperature, luminosity, power, electrical conductivity, radioactivity, coulomb potential or wave length (i have no idea what im talking about) will ALL fall at the same rate.
What is centripetal force? Where does it act towards?
Centripetal force is the force that acts upon any object that moves along a curved path. The force acts towards the centre of curvature (or the axis of rotation), centripetal force is need by all objects travelling in circular motion.
Define density and state how you would calculate it.
Density is the amount of matter in a certain amount of space. In other words how squashed up something is. Density (kgm⁻³ or gcm³) = mass (kg or g) ÷ volume (m³ or cm³)
State the difference between elastic and non-elastic collisions.
Elastic collisions conserve all their kinetic energy and momentum (i.e no energy is 'lost' in the form of heat or sound etc.) where inelastic collisions lose energy to the surroundings.
State Hookes law.
F = kx where, k = the spring/stiffness constant (lol) and x = the extension.
State the rule used in basically all momentum questions (Either than the equation)
For a closed system, the momentum is conserved providing that no external force intervenes (including friction.)
What is a Fossil fuel?
Fossil fuels are fuels made by the remains of dead animals and plants formed millions of years ago. These include natural gas, coal, oil.
Define friction
Friction is the force that opposes one surface moving -or trying to move- over another surface. Friction is due to the microscopic roughness of all substances.
Whats the difference between plstic and elastic materials.
If a force is applied to a elastic material, the extension would bu porportional to the restoring force. The material would also return to its original form after the force is taken away. However, if a force is applied to a plastic material, there is no relationship between the restoring force and the extension. when the force is taken away, the material will become permenantly deformed.
What happens when an object collides with another object of a bigger mass (Assuming no friction)
If a smaller object collides into a bigger object, all the momentum is transfered from A to B but object A will bounce back from object B and object B will move forward at a slower velocity compared to the velocity of Object A before they collided.
State the difference between mass and weight
Mass is the amount of matter that an object contains, weight is the measure of the force of gravity that acts upon an object. weight depends on your location withen the universe, while mass is constant, and does not change by location (Unless you smash into an astoroid...)
Define Power. State the equation of power in terms of energy transfer (NOT electricity) and state the units its measured in.
Power is the rate of the transfer of energy. Power is measured in Watts(W) and has an equation of: Power(W) = Energy transfered(Work done)(J) ÷ time taken(s)
what is the difference between static and dynamic friction.
Static friction is friction that occurs between two or more bodies in contact while still at rest. It is a friction that opposes the movement of an object(s) from moving. Dynamic friction is friction that opposes movement of a body already in motion. Maximium static friction is always larger than dynamic friction.
What is meant by the term center of mass?
The center of mass of an object is the single point of an object where all the mass is considered to act from.
If your driving a car, what effects how fast you can go around a bend. Explain.
The friction force between the tyres and the road provides the centripetal force. Therefore the surface o the road would affect how fast you could go around a bend. It also depends on the mass of the car and the sharpness of the bend.
Define momentum and state its equation
The momentum of a body is a measure of the amount of effort needed to stop and object in motion. This can be calculated by: Momentum(P) = Mass(m) x velocity(ms⁻¹)
What happens when an object collides with another object of identical mass (Assuming no friction)
The momentum of object A is completly transfered to object B. This leaves object A stationary while causing object B to move at the same speed as object A.
Describe the pathway of a projectile.
The projectile follows a parabolic pathway.
Describe the process of nuclear fission.
Unstable radioisotopes are forced to decay by shooting neutros at then. This causes then to decay into lighter elements, releasing massive amounts of energy in the process. The heat generated by the nuclear fuel (usually uranium-235) is used to heat a coolant which boils into steam and turns turbines which are attached to a dynamo which converts kinetic energy into electrcal energy. Nclear energy→heat energy→kinetic energy→electrical energy
State the difference between a vector and a scalar. then give an example of a scalar then their equivalent vector
Vectors are quantities containing direction and magnitude Scalars are quantities that don't employ direction, just magnitude. examples of scalars: speed, distance etc examples of vectors: velocity, displacement etc
What happens when an object collides with another object of a smaller mass (Assuming no friction)
When a larger object collides with a smaller object, not all the momentum is transfered from object A to object B, therefore, object B will move forward while Object A continues to move forward but at a lower velocity.
Explain how banked tracks enable you to take a bend faster.
When the bank angle is zero, the only force providing the centripetal force is the friction of the tyres. The reaction force to the cars weight is vertically upwards, therefore will not influence the centripetal force. If the track was banked the reaction force to the car's weight is not vertically upwards. The vertical component is oppsite and equal to the car's weight but the horizontal component of the reaction force acts in the same direction as the centripetal force. Therefore the centripetal force is larger on a banked track, thus, you can take it at a higher speed.
What are the conditions for equilibrium?
When there is no resultant force on an object AND that there is no resultant moment.
What is meant by work? State the equation and the units its measured in.
Work is the amount of energy transferred when an object is moved from one position to another. Work done is measured in joules and: Work done(J) =Force(N) x Distance(m), in the direction of the force.
Describe the following in projectile motion: a.) Acceleration of object. b.) Velocity of object. c.) Horizontal componet of the objects velocity.
a.) Acceleration is due to the objects weight and always acts vertically downwards at 9.81ms⁻². b.) Velocity will always act in a direction that is a tangent to it parabolic pathway. c.) The horizontal componet of velocity is not affected by gravitational accelerationas they act in different direactions, (changing the directionof the vector but not its magnitude), therefore the horizontal motion is equal in all parts.
Discuss the advantages and disadvantages of hydroelectricity.
a.) Advantages- Renewable energy source, no green house gases released. b.) Disadvantages- Expensive, Land must be flooded therefore can potentially damage wildlife habitats.
State the advantages and disadvantages to geothermal energy.
a.) Advantages- Renewable energy source, no greenhouse gases released. It is quite long lasting. b.) Deep drilling into hot rooks is difficult and expensive. Not alot of locations with hot rocks shallow in the crust.
Discuss the advantages and disadvantages of nuclear fission.
a.) Advantages- high energy density, no production of CO₂ b.) Disadvantages- radioactive waste material have very long half life's, thus need to be disposed of properly, risk of meltdowns, expensive to decommision.
Discuss the advantages and disadvantages of Fossil fuels.
a.) Advantages- readily available, and high enery density. b.) Disadvantages- Contribution towards global warming and releases pollutants and causing acid rain. Fossil fuels are non-renewable.
a.) How would you find the mass of a liquid with a unknown density? b.) How would you find the volume of a irregular shaped solid with a unknown density?
a.) Put an empty measuring cylinder on a top pan balance,take a reading. Put the measuring cylinder with the liquid onto a top pan balance, take a reading. subtract the first reading from the secound to obtain the mass of the liquid. b.) This is called the displacement method. Pour a specific volume of water into a measuring cylinder that can completely submerge your object. Take a reading of the volume of water. Now add the object into the measuring cylinder and make sure its fully submerged by water. Take a secound volume reading. Subtract the initial volume reading from the secound volume reading to get the volume of the object.
State the factors that affect the stability of an object
a.) ow high the center of mass is located at in relation to the height of the object. b.) idth of an object's base.
State the equation for the period of a pendulum, and rules for timing oscillations.
a.) period of a pendulum = 2π√(L÷G) where, L= length of pendulum and G = gravitational acceleration. b.) Make the oscillations as small as possible, to avoid air resistance influencing the results. Use a fiducial marker, to avoid parrallx error. Time at least 10 oscillations then divide it by the number of oscillation to decrease uncertainty due to reaction time. Repeat experiment at least 5 times and take a average.
Under what conditions will the centripetal force must increase to keep the object in circular motion?
a.) the speed of the object is increased (swinging a pendulum faster) b.) the mass of the object is increased (swinging a bigger pendulum) c.) the radius of circle in which the object is traveling in is decreased. ( Swinging a pendulum with only half the length of string)
what does the gradient on a speed-time graph represent?
acceleration (ms⁻²)
State Newton's 2nd law
an unbalanced force will cause an object to accelerate in the direction of the net force. the acceleration of the object can be calculated by: F = ma where, F=the resultant force, m=the mass and a= acceleration
state the relationship between distance speed and time state the relationship between time, velocity and displacement.
distance (m) = speed (ms⁻¹) × time (s) Displacement (S) = velocity (v) × time (t)
What does the area between the line and the x-axis represent?
distance traveled (m)
State Newton's 3rd law
if object A exerts a force on object B, then object B (simultaneously) exerts an equal but opposite force on object A. In other words, every action has an equal and opposite reaction. (exception of circular motion)
