05 Forces, movement and shape

Question 1

What is a contact force? [2 points]

Answer 1

A push and a pull; an applied force

Question 2

Which way does friction act to motion?

Answer 2

the opposite direction.

Question 3

What does friction do? [2 points]

Answer 3

Ofcten causes things to heat up
and is often the reason why things stop moving.

Question 4

how can friction be reduced? Name 3 points.

Answer 4

with lubricants; by riding on a cushion of air; or travelling on a low-fricion surface

Question 5

What is the name of the friction caused when moving through a fluid?

Answer 5

Drag.

Question 6

What is drag?

Answer 6

The friction caused when moving through a fluid.

Question 7

What is drag affected by? [3 points]

Answer 7

object’s shape
fluid it travels in
speed

Question 8

what is the name for the weight we feel?

Answer 8

gravitational pull

Question 9

what do all masses do?

Answer 9

attract other masses.

Question 10

what happens when an object rests on a solid?

Answer 10

it feels a reaction force 90* to the surface.

Question 11

what is the name for the force that works equal and opposite to the force of the object pushing on the surface?

Answer 11

normal reaction force.

Question 12

is thrust a reaction force?

Answer 12

yes

Question 13

how does thrust occur? [2 points]

Answer 13

when a mass is pushed out to the back of something, causing the object to move forwards.

Question 14

what does tention act in?

Answer 14

springs, chains and cables when they are stretched

Question 15

which way does the force act along for tension?

Answer 15

parallel (i.e. along) the string

Question 16

what is the stretching force proportinoal to ?

Answer 16

the extension

Question 17

define lift:

Answer 17

lift is the force produced due to the flow of a liquid over and aerodynamic surface.

Question 18

which 2 forces is lift often confused with?

Answer 18

upthrust and air resistance

Question 19

how does upthrust occur? [2 points]

Answer 19

when an object is submerged in fluid, and it is the force that causes an object to float (buoyancy)

Question 20

where does electrostatic force act between?

Answer 20

charged objects

Question 21

give the equation of newtons’ second law

Answer 21

F=ma

Question 22

what can g mean in the equation W=mg? [2 points]

Answer 22

can mean:
- the gravitational field strength (g=10N/Kg)
OR
- the acceleration due to gravity (g=10m/s^2)

Question 23

what does any object with mass have?

Answer 23

a gravitational field surrounding it

Question 24

true or false: any 2 objects with mass will attract each other?

Answer 24

true.

Question 25

true or false: the closer the objects, the weaker the gravitational force:

Answer 25

false. the closer the objects, the STRONGER the gravitational force

Question 26

what is mass?

Answer 26

a measurement of how much stuff makes up an object

Question 27

what is weight?

Answer 27

a measurement of how hard a gravitatinoal force pulls on that mass.

Question 28

define terminal velocity:

Answer 28

the constant speed and object reaches when drag is equal and opposite to the force of gravity acting upon the object.

Question 29

what happens at terminal velocity?

Answer 29

the object no longer accelerates, but continues falling at a constant speed

Question 30

Give and explain the 3 steps that explain a falling object? [6 points]

Answer 30

1. Initial fall: object accelerates due to gravity 2. Increasing resistance: as speed increases, air resistance builds up. 3. Balance: when aire resistance equal gravity, and the object stops accelerating. (not it has reacher terminal velocity.)

Question 31

give the 4 points affecting termnal velocity:

Answer 31

surface area shape mass air density

Question 32

define stopping distance:

Answer 32

the total distance a vehicle travels from when the driver sees a hazard to when the vehicle stops

Question 33

what is the equation for stopping distance?

Answer 33

stopping distance = thinking distance + braking distance

Question 34

define thinking distance:

Answer 34

the ditnce travelled from when the driver sees the hazard to when the vehicle stops

Question 35

give three factors that affect thinking distance:

Answer 35

speed age visibilty (tiredness/ concentration/ drugs/ alcohol)

Question 36

define braking distance:

Answer 36

the distance from when the brakes are applied until the vehicle stops

Question 37

give 3 factors that affect braking distance:

Answer 37

aftf: spped mass of the vehicle raod surface tires brakes slope

Question 38

how do thinking and speed relate?

Answer 38

TD increased linearly with speed

Question 39

how do braking distance and speed relate?

Answer 39

BD increases with the square of speed

Question 40

what does hooke's law state? [2 points]

Answer 40

that the extensino of a spring or a wire is proprtional to the load, to the force that is causing the extension

Question 41

what is the equatin linking force applied, spink constant and extension?

Answer 41

F=kx where F is force applied (N) k is spring constant (N/m) x is the extension (m)

Question 42

what is the sping constant also reffererd to as?

Answer 42

the 'stiffness of the spring'

Question 43

what is the srping constant measured in?

Answer 43

Newtons per metre

Question 44

what does a large sping constant mean?

Answer 44

very stiff spring

Question 45

i have a loose spring. it the spring constant loose or stiff?

Answer 45

loose.

Question 46

define elastic limit

Answer 46

point where the spinr gsotp behaving elastically and behaves plastically

Question 47

how do you avoid parallax? [2 points]

Answer 47

read off the measurement at eye level (and use a pointer)