PHYSICS

Question 1

How is energy transferred?

Answer 1

Electrically

Mechanically

Radioactively

With light

With Sound

Question 2

Describe a “system”

Answer 2

A system is a word for a single object or a group of objects E.g., air in a piston

Question 3

What is a “closed system”?

Answer 3

A system in which energy cannot enter or leave. The net change in a closed system is always zero. E.g., a thermos is ‘an isolated system’ - it’s not perfect because it gradually loses heat to the surroundings.

Question 4

What is a force?

Answer 4

A force is a vector quantity: - it has velocity - and it has direction E.g., a spaceship using thrusters to accelerate (change speed) or it is nudged off course by an asteroid

Question 5

What is a scalar?

Answer 5

Something that only has magnitude E.g, speed Quantity of apples temperature height

Question 6

What is a vector?

Answer 6

Something that has direction and speed

Question 7

What is a contact force?

Answer 7

When objects are actually touching each other

Question 8

What is an example of a non-contact force?

Answer 8

Gravity
Electrostatic forces
Magnetism

Question 9

What is gravity?

Answer 9

A force or attraction between massive objects. E.g., the moon’s gravitational pull affects the TIDES.
It is an acceleration: Earth’s gravity is 9.8 m/s/s or rounded to 10 m/s/s/. (also written as m/s^2 (metres per second squared)

Question 10

What is Newton’s Second Law of Motion?

Answer 10

(unbalanced)
Force = mass x acceleration

[Force is measured in NEWTONS]
[Mass is measured in Kg]
[Acceleration is measured in m/s/s]

Question 11

What happens when the resultant force is zero?

Answer 11

A system is in equilibrium (no change in speed or direction)

Question 12

What is the formula for acceleration?

Answer 12

acceleration= change in velocity / change in time taken

Question 13

What is weight measured in?

Answer 13

NEWTONS

Question 14

What is mass measured in?

Answer 14

Kg

Question 15

What is the formula for weight?

Answer 15

Weight (N) = Mass (Kg) x Gravitational Field Strength (N/Kg)

Question 16

What is resultant force?

Answer 16

When more than one force acts on an object, this is seen as a single force

Question 17

What is ‘work’ to a physicist?

Answer 17

When a force causes an object to move

Question 18

What’s the formula for WORK DONE?

Answer 18

WD = Fs

Work done = Force x distance (s)

WD is measured in Joules

Force in Newtons

Distance in metres.

Question 19

What happens when ‘work is done’?

Answer 19

Energy transfers in a system

Question 20

How do we change the shape of an object?

Answer 20

Use more than one force.

Question 21

What does ‘elastically deformed’ mean?

Answer 21

A temporary and reversible condition for an object undergoing stress: the object then returns to its original shape after the forces have been removed (squish a ball with two hands, pull a spring)

Question 22

What does ‘inelastically deformed’ mean?

Answer 22

When an object does NOT return to its original shape after forces acting on it have been removed.

Question 23

Describe the relationship of an elastic object to applied force

Answer 23

Directly proportional relationship

F = ke

F = force (Newtons)
k = the spring constant (Newtons per metre) e = extension (in metres)

Question 24

What is the limit of proportionality?

Answer 24

This is when the extension of a spring is no longer proportional to the force applied

Question 25

What is the spring constant?

Answer 25

How easy it is to stretch or compress a spring: a higher constant = a stiffer spring.

Force = spring constant x extension
F = k x e

Which means that
k = F/e (the spring constant is found by the force acting on it divided by the extension of the spring)

Question 26

What is the difference between ‘distance’ and ‘displacement’?

Answer 26

Distance is how far an object has moved. It is a scalar. Displacement is how far an object has moved from its original point. It is a vector.

Question 27

How do we calculate distance travelled?

Answer 27

s = v t

Distance (m) = velocity (m/s) x time (s)

s has replaced d for distance. Go figure.

Question 28

If an object is going around the bend at a constant speed what happens to its speed and velocity?

Answer 28

Speed is the same, but its velocity changes because it is changing direction. Turning in a circle implies that its velocity is changing all the time.

Question 29

What is Newton’s First Law (of motion)?

Answer 29

An object will remain in the same state of motion unless acted upon by an external force.

Question 30

What is inertia?

Answer 30

The tendency of an object to continue in the same state of motion.

Think of kids at the back of a class.

Question 31

What is the formula for acceleration?

Answer 31

a = (v² - u²) / (t₂ - t₁)

or a = change in v / change in t

Question 32

What is the formula of density?

Answer 32

Density = mass (Kg) / volume (m3)

density unit = Kg / m³

Question 33

What is the equation for CHARGE FLOW (electricity)?

Answer 33

Q = I t

Q = charge flow (COULOMBS)

I = current

t = time in secs

Question 34

Equation for Potential difference in terms of current and resistance

Answer 34

V = IR

Question 35

What is an Ohmic resistor?

Answer 35

The resistor is directly proportional to the potential difference at constant temperatures

Question 37

What is a thermositor?

Answer 37

Heat sensitive resistor

Resistance decreases as temperature increases