Physics MS notes from ppqs for all topics

Question 1

when the question asks you to draw a line if air resistance increases on a speed time graph, where should the line be placed

Answer 1

below the original line because

The speed is always less than the no–air-resistance case, so line Y lies below line X and acceleration decreases so flattens

Question 2

at one point a bungee jumper reaches her maximum speed- whats her average acceleration? what can be said abt the forces

Answer 2

0

forces are balanced

Question 3

why is acceleration always 9.8m/s^2 when someone falls from somewhere initially

Answer 3

because its the gravitational field strength and they experience freefall

Question 4

how does a graph show decreasing acceleration

Answer 4

decreasing gradient

Question 5

when does the object reach maximum height on a velocity-time graph? How do you find the time from the graph or calculation?

Answer 5

Maximum height when velocity = 0 m/s
On v-t graph: time where line crosses the time axis (v=0).
Calculation: t = u / g (initial vertical velocity (so like the top value on y axis) u divided by acceleration due to gravity g).

Question 6

what is the increase in gravitational potential energy of the object?

Answer 6

(the work done by the person on the object)J

Question 7

explain in terms of particles why it is hard to compress a liquid

Answer 7

-particles of liquid are touching/close to eachother

-forces of repulsion between particles of liquid are large

Question 8

whats the relationship between pressure and depth? whats the equation for it?

Answer 8

they have a positive correlation- the deeper the liquid, the higher the pressure

change in p= (density) × g (gravity) × Δh (vertical depth difference).

Question 9

whats the equation for pressure due to water?

Answer 9

pgh-density x 9.8 x height

Question 10

suggest a reason why a force of 8800N can’t lift objects of weight 8800N

Answer 10

-initial force has to be greater than 8800 to start motion
- the upwards force just balances the weight so no movement

Question 11

why is the total pressure often greater than what u calculated

Answer 11

atmospheric pressure/ liquid pressure

Question 12

state two energy resources for which the sun is the main source

Answer 12

two from:

fossil fuels

biofuels

solar panels

Question 13

What is the conservation of momentum equation for two objects separating (e.g., spring pushing trolleys apart) when initially at rest?

Answer 13

Total momentum before = total momentum after

Question 14

whats the equation for momentum

Answer 14

Momentum (p) = mass × velocity
p = m v

kgm/s

Question 15

A ball is dropped from height $h$. Ignore air resistance.

What is the equation for its maximum speed just before hitting the ground?

Answer 15

Key principle:
Conservation of energy
Gravitational PE → Kinetic energy

Equation:

mgh= 1/2mv^2

v= √2gh

Question 16

state the two conditions necessary for an object (helipcopter) to remain at equilibrium

Answer 16

1. no resultant force
2. no resultant moment

Question 17

whats the spring constant equation

Answer 17

F(force)=k(constant)x (equation)

Question 18

define the moment of a force and describe the effect it measures

Answer 18

force x perpendicular distance from pivot

measures turning effect of the force

Question 19

explain what is meant by centre of gravity

Answer 19

point where all the weight seems to act

Question 20

equation for power

Answer 20

work done or energy transferred/ time taken

Question 21

Uniform rectangular block, base side L, weight W, centre of gravity at centre.
Calculate moment of weight about a base corner (pivot).

Answer 21

Moment = W × (L / 2)

Perpendicular distance = half the base length (horizontal distance from corner to CoG).

Question 22

forces may produce changes in the size and shape of an object - state two other changes that forces may produce

Answer 22

velocity

acceleration

Question 23

what makes something an unstable structure

Answer 23

when the centre of gravity isnt above the base or if theres potential that it will tilt and produce a moment

Question 24

describe how moment is calculated

Answer 24

moment = force x distance
nm

Question 25

uses of radio waves

Answer 25

bluetooth astronomy RADAR wifi

Question 26

in what two scenarios does velocity change

Answer 26

if direction changes if magnitude changes

Question 27

explain why there must be a resultant force when a motorcyclist travels around a bend

Answer 27

because there is a change in velocity/ there is acceleration which means theres also a force

Question 28

Explain, in terms of forces, the changes in motion from when the parachutist leaves the balloon until reaching terminal velocity (point A)

Answer 28

Initially there is acceleration downwards due to gravitational force (air resistance ≈ 0) Air resistance increases as speed / velocity increases Resultant downward force decreases / acceleration decreases Constant speed (terminal velocity) when air resistance = weight / gravitational force

Question 29

what is meant by limit of proportionality?

Answer 29

point where extension stops being directly proportional to the load