mechanics

Question 1

what is newtons second law of motion?

Answer 1

F = MA
force (N)
Mass (Kg)
acceleration (m/s2)

Question 2

what is the accelaration of gravity?

Answer 2

9.81 m/s2

Question 3

what is the force of a 20kg object held above ground?

Answer 3

accelaration of gravity = 9.81

f=ma
f = 20x9.81 = 196.2 N

Question 4

what is a newton in SI units?

Answer 4

kg x m/s2

Question 5

what is inertia?

Answer 5

if an object is stationary or moving at constant velocity it tends to resist changes to its motion.
hence force needs to be applied for acceleration/ deceleration.

newtons 1st law of motion

Question 6

how much in grams is 1 newton of force equivalent too (i.e. based on gravity)

Answer 6

1 N = 10.2g of force

Question 7

what is the equation for momentum?

Answer 7

momentum = mass x velocity

Question 8

what is the law of conservation of momentum?

Answer 8

The momentum of all objects before the collision = the momentum of all objects after collision
(provided there is no net external forces acting on object)

e.g. 2 balls collide - total momentum after = total momentum before.

Question 9

what is newtons first law of motion?

Answer 9

in absence of external forces an object will remain at rest or constant velocity.
i.e. inertia
(requires driving force or friction for acceleration/ decelaration)

Question 10

what is newtons 3rd law of motion?

Answer 10

for every force there is equal and opposite force acting on an object.

Question 11

what is the formula for pressure derive the SI units…

Answer 11

force / area
measured in pascals

N/m2
N= kgms-2

therefore
Kgms-2/m-2
= kgm-1s-2

Question 12

a balloon is filled with air at a force of 10N. 4 holes are made each of 0.05m2. what is the pressure of the air leaving the balloon?

Answer 12

all wall of the balloon will exert equal pressure of 10m2
the pressure leaving will be equal in all holes
0.05x4 = 0.2
10/0.2 = 50 pascals
50/4 = 12.5 pascals per hole

Question 13

how can you manipulate the syringe you use to give more pressure?

Answer 13

A smaller syringe gives higher pressure because same newtons of force over smaller area.

alternatively to push a larger syringe it may need more force to create the same amount of pressure

Question 14

how is the pressure in a column of liquid calculated?

Answer 14

Pressure = density of liquid x height (m) x accelaration of gravity

P= pgh

(in an angulated column, it is the vertical height that matters)

if this column is open to the atmosphere, the atmospheric pressure can be added on
P = pgh + atmP

or can add whatever other pressure may be exerted on the column.

Question 15

how is force a column of liquid produces calculated?

Answer 15

pressure of a column = pgh
P=N/m2
therefore N= Pm2
so force = pgh x m2

Question 16

what is the equation for work done?

Answer 16

work = force x distance

work = pressure x volume

• e.g. how much energy needed to push a column of pressure by a certain volum

Question 17

what is energy?

Answer 17

the capacity to do work
measured in joules

Question 18

what is the equation for power?

Answer 18

workdone / time

joules / second

Question 19

derive joules as an SI unit…

Answer 19

force x distance
N = kgm/s-2
distance = m

kg.m2.s-2

Question 20

how does a hydraulic lift work?

Answer 20

workdone can be transferred from one unit to the next

imagine 2 columns of liquid -

work done = force x distance

first column has minimal force needed as small cross sectional area however is pushed down over a large distance

this can lift the other larger column (larger cross sectional area) over a small distance in height.

Question 21

how do airbags and seatbelts work?

Answer 21

air bag increases contact surface - this will reduce the pressure.
pressure = N/m2

seat belt will increase the stopping distance due to stretch.

joules energy = N x m2
joules/ m2 . the larger the stopping distance the less force exerted on body at one time i.e. discipitated over a larger distance.

Question 22

what is the difference between gauge pressure and absolute pressure?

Answer 22

gauge pressure = pressure relative to atmosphere. i.e. when a cylinder of gas is empty, gauge pressure reads 0

absolute pressure = gauge pressure + atmospheric pressure

Question 23

what type of pressure is blood pressure?

Answer 23

gauge pressure - relative to atmospheric

Question 24

define force…

Answer 24

vector quantity i.e. has magnitude and direction
which can be applied to an object to cause it to accelerate/ decelerate

Question 25

Are you more likely to dislodge a
blockage in a cannula when using
a 2 or 20 mL syringe?

Answer 25

a 2 ml syringe, as pressure is force over area. the 2 ml syringe has a
smaller cross-sectional area so the force applied by the thumb is spread
over a smaller area generating a higher pressure.

Question 26

is atmospheric pressure constant?

Answer 26

no.
atmospheric pressure is created by the force of gravity acting on the
molecules that make up the atmosphere

therefore atmospheric pressure
will depend on the height of the atmosphere and its density.

this means atmospheric pressure will fall with altitude and rising temperature.