Untitled

Speed\=

distance÷time (m/s)

What is the shape of a distance-time graph when the object is at rest?

a horizontal line

What is the shape of a distance-time graph when the object is moving with constant speed?

a slanted line with a constant gradient

What is the shape of a distance-time graph when the object is moving with changing speed?

a curved line

What is the distance traveled for motion with constant acceleration in a speed-time graph?

the area under the graph

If a body accelerates its speed-time graph will have a...

positive gradient

If a body decelerates its speed-time graph will have a...

negative gradient

What is the difference between speed and velocity?

Velocity is a vector while speed is scalar. Velocity has a direction.

a \=

∆v÷t or (v-u)÷t (m/s²)

Speed (on a distance-time graph) \=

the gradient

Acceleration (on a velocity-time graph) \=

the gradient

On a speed-time graph, a straight line with a positive gradient means...

constant acceleration

On a speed-time graph, a curved line with a positive gradient means...

changing acceleration

Deceleration

negative acceleration

On velocity-time graph the area under the graph is

the distance travelled

The mass of a body \=

the number of particles it has

Weight is a \_____________ force

gravitational

What is the difference between mass and weight?

Weight is affected by gravitational field strength

W(Weight) \=

m×g

How do you compare weights using balance?

You put a weight on each side of the balance then whichever way the balance leans is the heaviest.

What is 'inertia'?

It is the idea that if a force is applied to an object, it will not immediately reach a high speed because it requires time to accelerate, as shown by the formula F\=ma.

Weight (definition) \=

A body's mass multiplied by the strength of the gravitational field around it.

ρ \=

mass ÷ volume (kg/m³)

Describe an experiment to determine the density of a liquid and of a regularly shaped solid.

Find the mass by weighing the object on a scale and then use a measuring cylinder to find the volume. Then divide the mass by the volume to get the density in (g/cm³)

Describe the determination of the density of an irregularly shaped solid by the method of displacement.

First, fill a Eureka can to the level of the spout, then lower the solid into the water. Pour the water collected out of the spout into a measuring cylinder. That is the volume of the solid. Then, weigh the mass and apply the density formula (ρ \= m÷V) to calculate the density.

How do you predict whether an object will float based on density data?

Compare the density of the object and the density of the liquid; if the liquid has a greater density it will float.

A force may produce a change in \____ \___ \_____ of a body.

size and shape

A Resultant Force

A single force representing all the forces acting on a body.

Describe the ways in which a force may change a body.

push, pull, change shape and change direction

If two or more forces are acting on the same line then the resultant force is equal to...

the sum of the forces

If there is no resultant force on a body it...

either remains at rest or continues at constant speed in a straight line

Friction \=

the force between two surfaces which impedes motion and results in heating

Air resistance \=

a form of friction

State Hooke's Law.

the force (F) needed to extend or compress a spring by some distance (e) is proportional to that distance.

F (Hooke's Law) \=

k×e (N)

What is the significance of the 'limit of proportionality' for an extension-load graph?

Any extension-load graph must eventually end in a curve due to the limit of proportionality'.

What is the 'limit of proportionality'?

when a spring's extension is not directly proportional to the force used on it anymore.

F \=

m×a (N)

Describe qualitatively motion in a circular path due to a perpendicular force

Motion in a circular path happens when a body moves in a direction while another perpendicular force pulls it inward toward a center. In electrons this is the electrostatic force that keeps the atoms together; in our solar system it is the gravity of the sun.

The moment of a force \=

the turning effect of a force around a fixed point called a pivot.

What are some examples of moments?

opening a jar, wrenches, bicycles

Force or distance from the pivot is proportional to the...

moment of a force

moment \=

force × perpendicular distance from the pivot

Apply the principle of moments to the balancing of a beam about a pivot

If a beam is on top of a pivot in order to balance it the moments on both sides of the pivot must be balanced

When there is no resultant force and no resultant turning effect...

a system is in equilibrium and will remain in its current state.

What is a plane lamina?

A body whose mass is concentrated in a single plane

Describe an experiment to determine the position of the center of mass of a plane lamina.

Hang up the object. Suspend a plumb line from the same place. Mark the position of the thread. The center of mass is along the line of thread. Repeat the above steps with the object suspended from different places. The center of mass is where these lines cross.

Describe qualitatively the effect of the position of the center of mass on the stability of simple objects.

The lower the center of gravity of an object is, the more stable it is. Objects with a higher center of gravity are easier to topple than objects with a lower center of gravity. An object with a big base area is less likely to fall or topple over, than an object with a small base area. Furthermore, these two factors combine to decide the stability of an object. An object would fall over if its center of gravity does not pass through its base when it is tilted.

Vectors have a

magnitude AND direction

Scalars have a

magnitude and NO direction

Give 3 examples of a vectors.

acceleration, displacement, momentum, force, weight

Give 2 examples of scalars.

speed, distance, mass

What is momentum?

the quantity of motion of a moving body, measured as a product of its mass and velocity.

What is an impulse?

a force acting briefly on a body and producing a finite change of momentum.

momentum \=

mass × velocity (kgm/s)

impulse (equation)\=

∆momentum

Ft \=

∆m (kgm/s or Ns)

What is the law of momentum conservation?

For a collision or explosion occurring between object 1 and object 2 in an isolated system(providing no external forces act) the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision. That is, the momentum lost by object 1 is equal to the momentum gained by object 2.

work done \=

energy transferred

If a constant force of, magnitude F, acts on a point that moves distance s,in the same direction of the force, then what is work?

F×s

Work done \=

F×d (J)

W \=

∆E (energy transferred)

Power (definition)\=

a measure of the rate at which work is done

P \=

∆E÷t (W)

Power is measured in...

Watts

How can useful forms of energy be obtained from chemical energy stored in fuel? Also, what are it's advantages and disadvantages?

We can obtain useful energy from fuel by burning it. The heat from the fuel is used to make steam which then turns a turbine. This produces electricity. This is simple and cheap however the waste created is bad for the environment. As there is a limited supply of fuel it is also non-renewable.

How can useful forms of energy be obtained from hydroelectric dams? Also, what are it's advantages and disadvantages?

The water behind the dam pushes a turbine which turns a generator to produce electricity. This is environmentally friendly and is renewable, however, it is expensive to produce and requires a large amount of naturally flowing water in order to function.

How can useful forms of energy be obtained from geothermal resources? Also, what are its advantages and disadvantages?

Wells are drilled deep underground to extremely hot rocks.Water is poured down these wells and it returns to the surface as steam. This steam turns a turbine which creates electricity. It is renewable (the steam can be condensed then sent back down) and does not produce greenhouse gases. However, few sites are capable of producing geothermal energy and the power produced from such sites may not justify the expenditure on it.

How can useful forms of energy be obtained from nuclear fission? Also, what are it's advantages and disadvantages?

In nuclear fission, unstable isotopes are encouraged to split in a controlled environment. This produces heat which is used to turn water into steam which powers a turbine. This turbine makes electricity. While this produces a large amount of power and no carbon dioxide is produced, the damage of a meltdown is huge and the uranium used is non-renewable.

How can useful forms of energy be obtained from heat and light from the Sun? (solar cells and panels) Also, what are it's advantages and disadvantages?

Trapped heat from the sun uses photons to knock electrons free from atoms, generating a flow of electricity. This gives a nearly infinite supply of renewable power with little environmental impact. Unfortunately, they are also expensive and only work in the daytime.

How can useful forms of energy be obtained from the wind? Also, what are it's advantages and disadvantages?

Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity. While, wind energy is renewable, it is more expensive than fossil fuels and causes more noise.

What is the source of energy for all our energy resources? (except geothermal, nuclear and tidal)

The Sun

The Sun releases energy via...

nuclear fusion

efficiency \=

useful power output/power input *100

What is the law of conservation of energy?

The total amount of energy remains constant in an isolated system. Energy can neither be created nor destroyed, but can be changed from one form to another.

kinetic energy \=

½×m×v²

change in gravitational potential energy \=

m×g×∆h

In any event or process the energy tends to...

dissipate

p \=

F÷A (N/m³)

pressure \=

the force per unit area

What does a mercury barometer look like?

an inverted glass tube standing in a bath of mercury

What is another name for a mercury barometer?

A Torricellian barometer

How does a mercury barometer measure air pressure?

Air pressure pushes down on the surface of the mercury, making some rise up the tube. The greater the air pressure, the higher the mercury rises.

A liquid's pressure beneath the surface is directly proportional to its...

depth and density

What is a manometer used for?

A manometer measures the difference between two different points of pressure. A manometer works by balancing the weight of a column of fluid between the two points of interest.

p (Pressure) \=

h×ρ×g

What are the distinguishing properties of a solid?

Its particles are very closely packed together because of that there is very little room to move around. Therefore, the particles vibrate one fixed position. It has a fixed shape and volume - very inflexible.

What are the distinguishing properties of a liquid?

Its particles are closely packed together, but there is still some "wriggle" room. Similar to solid, but particles still have some freedom to move around. It often fits the shape of the container - e.g. water put into a conical flask will have a different shape than water put into a cup.

What are the distinguishing properties of a gas?

Its particles are free to move around and move past one another. It also assumes the shape of the container it is put in.

Describe qualitatively the molecular structure of solids in terms of the arrangement, separation and motion of the molecules.

A solid's particles are close together in a regular lattice formation. The particles are not separate and vibrate in formation.

Describe qualitatively the molecular structure of liquids in terms of the arrangement, separation and motion of the molecules.

A liquid's particles are close together but in a random pattern. They do separate and move around each other.

Describe qualitatively the molecular structure of gases in terms of the arrangement, separation and motion of the molecules.

A gas' particles are far apart in any direction with no pattern whatsoever. They are completely separate and move randomly

The quicker a gas' particles move...

the higher its temperature

Relate the properties of solids to the forces and distances between molecules and to the motion of the molecules

The particles are very close together and have strong forces binding them so they cannot change shape/separate easily.

Relate the properties of liquids to the forces and distances between molecules and to the motion of the molecules

The distance between the particles is not as close as that of a solid's, but the particles are still close together, and the forces between the particles are still strong. This means that a liquid can change shape.

Relate the properties of gases to the forces and distances between molecules and to the motion of the molecules

The particles are far apart from each other and have weak forces acting on them. This means that a gas can easily change shape and be compressed.

Describe qualitatively the pressure of a gas in terms of the motion of its molecules

The motion of molecules in a substance causes the collision of these molecules on the wall of the container. This exerts a force on the walls of this container, which we define as pressure.

How does Brownian motion prove the kinetic molecular model of matter?

The larger particles are being passed around by

Describe Brownian motion in terms of random molecular bombardment.

Brownian motion is when particles in a suspension move randomly due to random bombardment by other particles

Explain pressure in terms of the change of momentum of the particles striking the walls creating a force.

Each molecule in a container moves along with constant velocity in a straight line, until it hits another molecule, or a container wall. The molecules exchange momentum, but the total momentum of the two molecules is conserved. When a molecule hits a wall, it bounces back and its momentum changes. The greater the number of molecules hitting a wall, the greater is the force on the wall. The pressure in the container is the magnitude of the normal force F on a wall divided by the surface area A of the wall.