The Newtonian World

Question 1

Newtons 3rd law should act on…

Answer 1

…different bodies.

Question 2

How do you find the mass of one ion?

Answer 2

Molar mass/ Avogardo constant

Question 3

What is meant by internal energy of the gas

Answer 3

is the sum of the random (distribution of) kinetic and potential energies of (all) atoms/molecules (in the system)

Question 4

Explain why the internal energy of the gas differs from that of its liquid phase

Answer 4

Comparison of kinetic energies in gas and liquid phases linked to temperature
Potential energy of gas phase is greater than PE of liquid phase / energy must be supplied to change liquid into gas phase..

Question 5

SHM:

How to find (max) velocity of an object.

Answer 5

v = 2 x pie x f x A

f-frequency
A-amplitude

Question 6

What is meant by geostationary orbit?

Answer 6

satellite is always vertically above the same point on the surface of the Earth/ planet

Question 7

You are provided with a small bottle of cooking oil and standard physics lab equipment. Describe an electrical experiment to determine the specific heat capacity of oil. State two sources of uncertainty in your measurement and discuss how these could be reduced.

Answer 7

Diagram showing:
-Oil in (insulated) container
-Electrical heater fully immersed in oil
-Thermometer / Temperature sensor
Electrical circuit:
-Ammeter in series , voltmeter in parallel with heater / joulemeter in parallel with heater
-Power supply /+ & - signs marked on wires
Measurements:
-Measure mass of oil /use known mass of oil,
-Measure change in temperature / initial and final
temperatures
-Measure current, pd and (fixed) time / energy
Calculation:
InputEnergy=E=Pt=VIt and c=E/m(changein temp)
Uncertainties:
-Temperature varies throughout oil - minimise by stirring
before taking temperature readings
-Some energy is required to raise temperature of the
container / heater (etc) - allow by including in calculation.
-Temperature will continue to rise after heater is turned off
– find max temperature.

Question 8

State three assumptions made in the development of the kinetic model of an ideal gas.

Answer 8

-Collisions with the walls/container/sides are elastic
-force between molecules is negligible / zero except during collisions
-Volume of the molecules is negligible compared to the volume of the container
-Time within a collision is negligible compared to time
between collisions

Question 9

Use the kinetic model of a gas and Newton’s laws of motion to explain how a gas exerts a pressure on the walls of its container.

Answer 9

• Momentum of the molecule changes when it collides with the wall
• Force on the molecule is rate of change of momentum (by N 2nd Law)
• (By N 3rd Law) Force on wall is equal to and opposite to the force on the molecule
• pressure = sum of forces (due to all molecules)/Area of wall

Question 10

Newton’s second law of motion

Answer 10

Rate of change of momentum (of a body) is proportional /
equal to the (net) force (acting on it)
and takes place in the direction of that force.

Question 11

What does Newton’s 3rd Law of motion mean about the relationship between the impulse experienced between the two particles during impact.

Answer 11

Force on B (due to A) is equal and opposite to force on A
(due to B)
time (of contact) / t is same for both AND Impulse = Ft
impulse on A is equal and opposite to impulse on B

Question 12

How to find orbital speed of satellite using: gravitational field strength, radius and velocity.

Answer 12

g = v^2 /r

Question 13

How to find period of the orbit of a satellite using r and v.

Answer 13

T= (2 x pie x r) / v

Question 14

Newton’s Law of gravitation

Answer 14

Force is proportional to the product of the masses and inversely proportional to the square of their separation

Question 15

Principle of conservation of linear momentum

Answer 15

Total momentum is constant/conserved

For a closed system/provided no external forces

Question 16

Explain what is meant by an inelastic collision

Answer 16

Some loss of kinetic energy

Question 17

State, in terms of force, the conditions necessary for the object to move in a circular path at constant speed.

Answer 17

resultant overall force acts (on object) perpendicular to the OR towards the centre of the circle

Question 18

Explain why this object is accelerating. State the direction of acceleration.

Answer 18

velocity OR direction is always changing

acceleration is in direction of force OR is towards the centre/perp. to velocity

Question 19

Centripetal force equation

Answer 19

F = mv^2/r

Question 20

What is Angular Frequency

Answer 20

angular frequency is product of 2x pie x frequency OR (2x pie)/period.

Question 21

How to find maximum velocity in simple harmonic motion.

Answer 21

v= 2x pie x f x A

Question 22

Boyle’s Law

Answer 22

pressure is inversely proportional to volume

for a fixed mass of gas at constant temperature

Question 23

Area under a force time graph…

Answer 23

…Impulse

Question 24

Describe the pattern of g field lines close to the surface of the earth.

Answer 24

• Field lines are parallel to each other
• Field lines are equally/evenly/uniformly/constantly spaced
• Field lines are perpendicular / vertical / right angles (to surface of the Earth)

Question 25

What is meant by resonance of a mechanical system.

Answer 25

• Resonance occurs when the driving frequency matches natural / resonant frequency (of system)
• the amplitude of vibrations / energy (transferred) is then a maximum

Question 26

State an everyday example of resonance.

Answer 26

-microwave (oven), Mirror in car, Washing machine,

Question 27

A constant mass of gas occupies a container of constant volume. Use the kinetic theory of gases to explain the increase in the force exerted on the walls of the container by the gas when its temperature is raised.

Answer 27

-Increase in temperature causes an increase in velocity / speed (of molecules)
-Collisions are more frequent
-Greater (rate of) change in momentum (in each collision with the surface)
Hence force increases

Question 28

State, in terms of force, the conditions necessary for an object to move in a circular path at constant speed.

Answer 28

resultant/overall force acts (on object) perpendicular to the velocity OR towards the centre of the circle

Question 29

State Newton’s first law of motion

Answer 29

A body will remain at rest or continue to move with constant velocity unless acted upon by a force

Question 30

State and explain at what point when weightlessness may occur, in a plane travelling in a loop.

Answer 30

At top of the circle

when the weight provides/equals the required centripetal force

Question 31

Explain how the speed of the bung remains constant even though there is a resultant force acting on it. Bung travelling in a circle. (circular motion)

Answer 31

Resultant force (F) acts at 90 degrees to motion / velocity of bung
so no work done is done by F (hence no change in speed)

Question 32

State two features of a geostationary orbit.

Answer 32

• Equatorial orbit

- Period is 24h/1day/same as Earth

Question 33

Define gravitational field strength.

Answer 33

Force per unit mass (at a point in a gravitational field)

Question 34

State Kepler’s third law.

Answer 34

The cube of the planets distance (from the Sun) divided by the square of the (orbital) period is the same (for all planets)

Question 35

State Newton’s law of gravitation

Answer 35

Force between two (point) masses is proportional to the product of masses and inversely proportional to the square of the distance between them

Question 36

State Newton’s law of gravitation

Answer 36

Force between two (point) masses is proportional to the product of masses and inversely proportional to the square of the distance between them

Question 37

The mass is in equilibrium. By referring to the forces acting on the mass and spring, explain what is meant by equilibrium.

Answer 37

• The resultant force is zero

- Forces are weight and force from the spring

Question 38

Explain what is meant by SHM.

Answer 38

• acceleration is (directly) proportional to displacement

- and is directed in the opposite direction to the displacement.

Question 39

Angular frequency

Answer 39

is product of 2x pie x frequency OR (2x pie)/period

Question 40

The frequency of the vibrating plate is kept constant and its amplitude is slowly increased from zero. The grains of sand start to lose contact with the plate when the amplitude is A0. State and explain the necessary conditions when the grains of sand first lose contact with the plate.

Answer 40

• This occurs at the highest point (top) of the oscillations

- When acceleration of plate equals/exceeds free fall acceleration /g/ 9.81

Question 41

Explain in terms of motion of the molecules of the gas why the volume of the gas must increase if the pressure is to remain constant as the gas is heated. If the temp is increased.

Answer 41

-(When gas is heated) molecules gain KE/move faster
this would cause more collisions/sec (with the walls)
collisions exert more force/greater change in momentum per collision
-For constant pressure fewer collisions/sec are required
-Constant pressure is achieved by the increase in volume OR with a bigger volume there are fewer collisions/sec

Question 42

Explain the term thermal equilibrium.

Answer 42

no net heat flow between objects

Question 43

State Boyle’s Law.

Answer 43

• pressure is inversely proportional to volume

- for a fixed mass of gas at constant temperature