Lesson 4

Question 1

Define speed.

Answer 1

Speed is the rate at which an object moves (ex. 100 km/h)

Question 2

Define velocity.

Answer 2

The speed travelled in a given direction (ex. 100 km/h due east)

Question 3

Define acceleration.

Answer 3

It is the change in velocity (ex. 9.8 m/s^2 downward)

Question 4

What did the Copernican revolution spark for sir Isaac Newton?

Answer 4

The discovery of the laws of motion and gravity

Question 5

Do all falling objects accelerate at the same rate?

Answer 5

Yes; everything on earth accelerates at 9.8m/s
- this means that if a falling object takes 1 second to reach the ground, it was falling at 9.8m/s, it it took 2 seconds, it was falling at 9.8m/s x 2, etc

Question 6

What does net force change?

Answer 6

It changes the momentum of an object (which generally means acceleration, i.e. velocity)

Question 7

What is a force?

Answer 7

it is a vector quantity (its direction matters)

- multiple forces can be applied to an object in different directions

Question 8

What is weight? What is mass? Are they the same thing?

Answer 8

Weight = the force that acts upon an object (mass x gravity)
Mass = the amount of matter an object has
Weight does not equal mass

Question 9

What is momentum?

Answer 9

mass x velocity

Question 10

How can weight change?

Answer 10

In the amount of gravity that is acting on an object and the motion of the object (particularly acceleration)
- ex. a 100kg object on earth moving downward will be 100kg on the moon if it is moving upwards

Question 11

What is angular momentum?

Answer 11

The rotational momentum of a spinning object

Question 12

What is net force?

Answer 12

The direction an object will go when all other forces are also applied (like a tug of war between a strong guy and a 5 year old)

Question 13

What is weightless free fall?

Answer 13

When the effects of acceleration are more powerful than the effects of gravity

Question 14

What does the law of conservation state?

Answer 14

a quantity cannot be created or destroyed, it can only be exchanged for something else

Question 15

What does acceleration upwards cause?

Answer 15

More gravity therefore more weight

Question 16

What does acceleration downwards cause?

Answer 16

Less gravity therefore less weight

Question 17

What were Newton’s Laws of Motion? (3)

Answer 17

1. an object moves at a constant velocity unless a net force acts to change its speed or direction
2. Force = mass x acceleration
3. for every force, there is always an equal and opposite reaction force

Question 18

What are the three laws of conservation? (3)

Answer 18

1. Law of Conservation of momentum:
   - the total momentum of interacting objects cannot change unless an external force is acting on them
2. Law of Conservation of angular momentum:
   - angular momentum = mass x velocity x radius of angular movement
   - as radius decreases, velocity increases and as radius increases, velocity decreases
3. Law of Conservation of energy:
   - energy is conserved but can be exchanged with objects and with other forms of energy
   - the total amount of energy of the universe was determined in the big bang and remains the same

Question 19

What are the three basic categories of energy?

Answer 19

1. kinetic energy (movement)
2. radiative energy (light and gravity)
3. potential energy (stored energy like electricity)

Question 20

What are the 4 types of forces?

Answer 20

1. gravitational
2. electromagnetic
3. weak
4. strong
   - these forces interact to create different kinds of energies

Question 21

What are the three subcategories of energy?

Answer 21

a. thermal energy: collective kinetic energy of the many particles in a substance (C, F or K)
b. gravitational potential energy: how gravity interacts with an object that has mass
- in space, an object has more gravitational energy when it is spread out than when it contracts
b. i. mass: a form of potential energy
- E=MC^2
- a small amount of mass can produce a large amount of energy

Question 22

Describe the universal law of gravity?

Answer 22

Every mass attracts every other mass

• attraction is directly proportional to the product of their masses
• attraction is inversely proportional to the square of the distance between their centres

Question 23

What can Newton’s third law help astronomers to do?

Answer 23

Estimate the mass of distant objects

Question 24

What effects do gravity have on orbits?

Answer 24

• total orbital energy (gravitational and kinetic) remain constant if there is no external force
• orbits can gain or lose energy by having a gravitational encounter or by experiencing friction or atmospheric drag

Question 25

What happens if an object gains enough orbital energy?

Answer 25

It can escape bound orbit to unbound orbit (escape velocity)

Question 26

What is the escape velocity from earth?

Answer 26

11 km/s from sea level

Question 27

How does the moon’s gravity affect earth?

Answer 27

• the shape of earth is bulged due to the moon’s gravitational pull
• it causes water to change tides
• the rotation of the earth is affected (it is slowed down due to the gravity of the moon pulling on earth)

Question 28

What is the size of the tide affected by? Which phase is associated with which tide?

Answer 28

The size of the tides is affected by the phase of the moon (where the moon is in relation to the sun)

• a spring tide (highest tide) is associated with new and full moons
• a neap tide (lowest tide) is associated with the first and third quarter

Question 29

What is tidal friction?

Answer 29

Friction with the rotating earth pulls the tidal bulges slightly ahead of the earth-moon line

Question 30

What does tidal friction have an effect on?

Answer 30

The length of a day

- it increases by 1 second every 50,000 years

Question 31

Is the rate of acceleration of an object dependent on its mass?

Answer 31

NO