P2.2 -Forces

Question 1

what happens in an interaction pair (N3)?

Answer 1

• forces act in opposite directions

- each force is the same magnitude

Question 2

what is newton’s third law?

Answer 2

“when two bodies interact, they exert a force upon each other that is equal in size, but opposite in direction”

Question 3

state three non-contact forces?

Answer 3

• gravity
• electrostatics
• magnetism

Question 4

how does gravity interact with objects?

Answer 4

attracts them

Question 5

how do electric charges interact with objects?

Answer 5

• attract and repel

Question 6

what is a field of a force?

Answer 6

the region where an electric charge, a magnetic material or a mass experiences a force

Question 7

how are forces represented?

Answer 7

with a force arrow

Question 8

where does a force arrow start on an object for a non-contact force?

Answer 8

the centre

Question 9

where do you draw contact force arrows from?

Answer 9

the point of contact

Question 10

use what you know about the structure of the atom to suggest why a non-contact force is produced within an atom

Answer 10

• there are electrons on the outsides of atoms.
• As you push them together they repel.
• This is an electrostatic force, which is a non-contact force.

Question 11

what is terminal velocity?

Answer 11

the velocity at which a body falls through a medium, when the drag acting on the body is equal to its weight

Question 12

what planes do we consider when explaining the motion of an object at an angle?

Answer 12

• the plane perpendicular to the slope

- the plane parallel to the slope

Question 13

what is air resistance?

Answer 13

when an object moves through air and collides with other air molecules

Question 14

what is tension?

Answer 14

the pulling force that a string or cable exerts when something or someone pulls in it

Question 15

what is friction?

Answer 15

• when two surfaces are touching and try to move against each other.

Question 16

how does friction work?

Answer 16

• Tiny bumps in the surface interlock (overlap or fit together). This creates a frictional force that opposes their motion.

Question 17

what kind of force is air resistance?

Answer 17

contact (air particles collide)

Question 18

what does a free body diagram show?

Answer 18

shows the forces acting on a single object

Question 19

what is a resultant force?

Answer 19

the force when two or more forces are added together

Question 20

what is a force?

Answer 20

a push of a pull

an attraction or repulsion

Question 21

what can a force do?

Answer 21

• change the shape of an object

- change the motion of an object

Question 22

what are forces measured in?

Answer 22

N (newtons)

Question 23

state one way in which the force of gravity is different to the electrostatic force

Answer 23

• gravity can only attract

- electrostatic force can attract and repel

Question 24

what happens when bodies interact?

Answer 24

• exert forces upon each other

Question 25

what does a free body diagram show?

Answer 25

all the forces acting on a single body

Question 26

what does it mean to resolve a force?

Answer 26

- work out how much of it acts in the horizontal plane | - work out how much of it acts in the vertical plane

Question 27

what is Newton’s First Law?

Answer 27

“A body will remain at rest, or continue to move at a uniform velocity, unless acted upon by a resultant force”.

Question 28

what is Inertia?

Answer 28

A measure of how difficult it is to change the velocity of a body (either from rest or when traveling at a uniform velocity)

Question 29

if an object has a higher mass, why does it have a higher inertia?

Answer 29

- more difficult to accelerate/change velocity

Question 30

what is componenticing?

Answer 30

seeing how much force is acting on specific planes

Question 31

what is the equation for force?

Answer 31

F = M x A | newton’s second law

Question 32

what is the unit for acceleration?

Answer 32

m/s^2 | meters per second squared

Question 33

define acceleration

Answer 33

the rate of change of velocity of a body

Question 34

if a body is travelling at a constant speed but a different direction, is it accelerating?

Answer 34

yes, as the velocity changes

Question 35

what is the equation for acceleration?

Answer 35

final velocity - initial velocity / time

Question 36

what does acceleration depend on?

Answer 36

- size of resultant force | - inertia (mass) of object

Question 37

what stays the same during circular motion?

Answer 37

- speed of the plane stays the same

Question 38

what changes during circular motion?

Answer 38

velocity continuously changes (direction)

Question 39

why is an object in circular motion continuously accelerating?

Answer 39

as it is constantly changing direction

Question 40

where does the centripetal force act?

Answer 40

towards the centre of the circle

Question 41

what does centripetal force change?

Answer 41

- the direction of velocity | - NOT SIZE

Question 42

what is free fall?

Answer 42

the fall of a body through a medium, without a drag producing device

Question 43

explain why terminal velocity is a constant

Answer 43

the weight of the body is balanced by the drag force acting upon it

Question 44

which planes are considered for a box on a slope?

Answer 44

- parallel to slope (where box tries to accelerate) | - perpendicular (where normal reaction force acts)

Question 45

what is the equation for momentum?

Answer 45

mass x velocity

Question 46

what is momentum a measure of?

Answer 46

how difficult it is to stop a moving body

Question 47

what is momentum measured in?

Answer 47

kgm/s (kilograms meters per second)

Question 48

what does momentum depend on?

Answer 48

- mass | - velocity

Question 49

is momentum vector or scalar

Answer 49

vector (has direction)

Question 50

what is the law of conservation of momentum?

Answer 50

the movement before is equal to the momentum afterwards

Question 51

what is an inelastic collision?

Answer 51

when energy is transferred to other sources

Question 52

what is an elastic collision?

Answer 52

when no net energy is transferred to other sources (which is not kinetic energy) ie. no energy lost as sound, light

Question 53

what happens when a stationary body is hit by a moving body

Answer 53

two bodies move off together

Question 54

what is the opposite force to the force of the Earth on a skateboarder

Answer 54

normal reaction force | force of skateboarder on earth

Question 55

what happens when two bodies push off each other?

Answer 55

bodies move away from each other

Question 56

what is work?

Answer 56

the transfer of energy

Question 57

what is work measured in

Answer 57

J (joules)

Question 58

what happens when work is done?

Answer 58

energy is transferred from one form to another

Question 59

what happens when you lift a body?

Answer 59

kinetic energy is transferred to gravitational potential energy

Question 60

what is the equation to calculate work done?

Answer 60

force x distance

Question 61

how much is one joule in newton meters?

Answer 61

1J = 1Nm

Question 62

what do we assume about distance?

Answer 62

it is covered at a constant velocity (zero acceleration) (zero resultant force)

Question 63

how does friction transfer energy?

Answer 63

out of a body (and transfers heat)

Question 64

what is power?

Answer 64

rate of transfer of energy

Question 65

how does a force applied transfer energy?

Answer 65

into a body

Question 66

what is the equation for power

Answer 66

energy / time

Question 67

what is power measured in?

Answer 67

Watts(W)

Question 68

how much energy is transferred during 1 watt (per second)

Answer 68

1 joule per second

Question 69

how is acceleration proportional to mass?

Answer 69

inversely proportional

Question 70

what is Newton’s Second Law?

Answer 70

“The acceleration experienced by a body is directly proportional to the resultant force acting upon it, and in the same direction” AKA ‘push something harder, accelerate faster’