Workbook 1

Question 1

Define Base Quantities

Answer 1

Base Quantities are seven fundamental quantities (invented and agreed upon by humans) that make up any known quantity.

Question 2

What are the two properties of Base Quantities?

Answer 2

They cannot be defined by any other physical quantity and they are accepted as being functionally independent of one another.

Question 3

Name the 7 base quantities

Answer 3

Mass, Length, Time, Electric Current, Temperature, Amount of Substance and Luminous Intensity.

Question 4

What are derived quantities?

Answer 4

Derived quantities are quantities formed by one or more base quantities.

Question 5

Define distance and displacement

Answer 5

Distance is a scalar quantity that refers to how much length an object covers during its motion whilst displacement is a vector quantity that refers to the linear distance away from its original position an object is.

Question 6

Define speed, velocity and acceleration

Answer 6

Speed is the rate of change of distance, velocity is the rate of change of displacement and acceleration is the rate of change of velocity.

Question 7

What is weightlessness?

Answer 7

Weightlessness occurs when there is no weight on the body, however, this can be experienced if the body is accelerated downwards with the same acceleration as that due to gravity.

Question 8

What is drag?

Answer 8

Drag is a mechanical force. It is generated by the interaction and contact of a body with the molecules of a fluid.

Question 9

Define viscosity

Answer 9

Viscosity is the fluid’s resistance to flow or change shape over a given time.

Question 10

What is terminal velocity?

Answer 10

Terminal velocity is the constant speed reached by a falling object when the resistance of the medium through which it falls prevents further acceleration. This is achieved when the weight of the falling object is equalled by the drag force.

Question 11

What is a projectile?

Answer 11

A projectile is an object which is propelled forward into the air or into space by the exertion of a force which ceases after launch.

Question 12

State Newton’s First Law of Motion.

Answer 12

Newton’s First Law of Motion states that a body at rest will remain at rest, while a moving body will keep moving at constant velocity unless acted upon by a resultant force. This is known as Inertia.

Question 13

State Newton’s Second Law of Motion.

Answer 13

Newton’s Second Law of Motion states that the resultant force exerted on a body is directly proportional to the rate of change of linear momentum of that body.

Question 14

Define the Newton.

Answer 14

It is the amount of force that causes a 1kg mass to accelerate at 1 metre per second squared.

Question 15

State Newton’s Third Law of Motion.

Answer 15

Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction. (These two forces are equal in magnitude but are opposite in direction, they also act on different bodies)

Question 16

What causes an impulse?

Answer 16

A change in momentum.

Question 17

State the Principle of Conservation of Linear Momentum.

Answer 17

The Principle of Conservation of Linear Momentum states that for a collision between two objects in an isolated system, the total momentum before is equal to the total momentum after provided no resultant, external forces act on the system.

Question 18

What happens in a perfectly elastic collision?

Answer 18

The kinetic energy of objects before collisions will be conserved. After collision, the sum of the kinetic energy of the objects will be the same as before, therefore no KE will be converted to other forms. After an elastic collision, bodies do not move off together.

Question 19

What happens in an inelastic collision?

Answer 19

The kinetic energy is not conserved, therefore some of the initial kinetic energy is converted to other forms of energy during the collision, resulting in less KE after the collision. In an inelastic collision, the bodies do move off together.

Question 20

What is an explosion?

Answer 20

An explosion is when two bodies start off together and then move in separate directions. (use sign convention)

Question 21

Define Energy.

Answer 21

Energy is defined as the capacity of doing work.

Question 22

How can we transfer energy?

Answer 22

By supplying heat or by doing work on the object.

Question 23

Distinguish between Potential Energy and Kinetic Energy.

Answer 23

Potential energy is the energy that an object has stored.(ex. GPE is the energy that an object has stored due to its place in a gravitational field). Kinetic Energy is the total work that was done to accelerate it from rest to the object’s present speed.

Question 24

Define Power.

Answer 24

Power is the rate of transfer of energy to an object.

Question 25

What is the equation for efficiency in terms of energy?

Answer 25

Efficiency is the useful energy output divided by total energy input times 100.

Question 26

State the conditions for circular motion.

Answer 26

A force directed towards the centre, or axis of rotation, and the object must have velocity directed perpendicularly to the force, i.e centripetal force.

Question 27

Define angular speed

Answer 27

This is the angle swept by the radial line per second.

Question 28

Define angular acceleration.

Answer 28

The angular acceleration of a rotating particle is defined as the rate of change of angular velocity.

Question 29

What provides the centripetal force in the situation of a car going round a bend?

Answer 29

The resultant frictional force between the tyres and the road surfaces.

Question 30

Why do banked surfaces allow for higher speeds in cars?

Answer 30

The centripetal force is not only provided by the resultant frictional force between the tyres and road surfaces. It is also provided by a component of the reaction.

Question 31

What provides the centripetal force when an object is at the top of a loop-the-loop?

Answer 31

The object’s weight and reaction.

Question 32

If an object is whirled in a vertical circle, where is the string most likely to break?

Answer 32

At the bottom since the string must generate the centripetal force and also support the weight of the object. Therefore, tension is greater at the bottom.

Question 33

State Newton’s Law of Gravitation.

Answer 33

Newton’s Law of Gravitation states that any two masses in the universe attract one another with a force that is directly proportional to the product of the masses and inversely proportional to the square of the distances between them.

Question 34

Why is the law said to be universal?

Answer 34

It applies anywhere in the known universe.

Question 35

Define weight.

Answer 35

Weight is the resultant gravitational pull on a mass due to another.

Question 36

What is gravitational field strength?

Answer 36

It is the force experienced by a unit mass when in a gravitational field.

Question 37

How does g vary on Earth?

Answer 37

Rock density; a mass tied to a string a the foot of a mountain will not hang vertically downwards but will be tilted slightly towards the mountain due to an attraction towards it.
Earth’s Shape; due to the fact that Earth is ‘squashed’ at the poles and wider at the equator. An object at the equator experiences a greater rotational speed. Therefore, due to its inertia, it experiences a fake force outwards which is in the opposite direction to the weight. This makes the object experience a smaller apparent weight, therefore having a smaller acceleration due to gravity.
Earth’s Rotation.

Question 38

Distinguish between Inertial Mass and Gravitational Mass.

Answer 38

Gravitational Mass is measured by comparing the force of gravity of an unknown mass to the force of gravity of a known mass whilst Inertial mass is found by applying a known force to an unknown mass, measuring the acceleration, and applying Newton’s Second Law.

Question 39

What is a gravitational field?

Answer 39

A gravitational field is a region around a mass where a gravitational force is felt.

Question 40

What do lines of force represent?

Answer 40

Lines of force represent the path taken by a unit mass if it is free to move in a gravitational field.

Question 41

What is the Uniform field?

Answer 41

The uniform field is one where the space between the field lines (density) is constant. This would cause masses to experience a constant force anywhere in the field.

Question 42

Define Gravitational Potential

Answer 42

The Gravitational potential is the potential energy per unit mass at a point in a gravitational field.

Question 43

What is the escape velocity?

Answer 43

The escape velocity is the velocity that needs to be given to an object to take it to a point where the gravitational pull on it is equal to zero.

Question 44

What is an equipotential?

Answer 44

An equipotential surface is a region or space where every point is at the same potential.

Question 45

State Kepler’s three planetary laws.

Answer 45

1. The law of ellipses states that the path of the planets about the sun is elliptical in shape, with the centre of the sun being located at one focus.
2. The law of Equal Areas states that an imaginary line drawn from the centre of the sun to the centre of the planet will sweep out equal areas in equal intervals of time.
3. The law of Harmonies states that the ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun.

Question 46

Distinguish between Polar-orbiting and geostationary satellites.

Answer 46

Polar-orbiting satellites are ones that travel low and go around the Earth several times a day, tracking various things such as weather. Geostationary satellites are ones that are situated high above the equator, they move with the same period of Earth (24 hours) and thus remain in the same spot. These are used mainly for communication purposes, i.e; gps.