Forces and Motion

Question 1

force

Answer 1

the action of one body on a second body

Question 2

air resistance

Answer 2

friction acting on an object moving through air

Question 3

friction

Answer 3

the force that acts when two surfaces rub over one another

Question 4

drag

Answer 4

friction that acts on an object as it moves through a fluid

Question 5

gravity

Answer 5

the force that exists between any two objects with mass

Question 6

terminal velocity

Answer 6

the greatest velocity reached by an object when moving through a fluid

Question 7

gravitational field formula

Answer 7

weight/mass

Question 8

equation connecting force, mass and acceleration

Answer 8

force = mass x acceleration

Question 9

momentum formula

Answer 9

momentum = mass x velocity

Question 10

impulse formula

Answer 10

force x time for which the force acts

Question 11

resultant force formula

Answer 11

change in momentum/time

Question 12

impulse

Answer 12

the change in an objects momentum

Question 13

resultant force

Answer 13

the sum of all forces acting on an object

Question 14

turning effect

Answer 14

when a force causes an object to rotate if there were no resistive forces

Question 15

pivot

Answer 15

the fixed point about which a lever turns

Question 16

moment

Answer 16

the turning effect of a force about a pivot

Question 17

moment formula

Answer 17

force x perpendicular distance

Question 18

When is an object in equilibrium

Answer 18

forces are balanced, turning effects must also be balanced

Question 19

equilibrium

Answer 19

when no net force or net moment act on a body

Question 20

principle of moments

Answer 20

when an object is in equilibrium the sum of the anticlockwise moments is equal to the sum of clockwise moments about the same point

Question 21

centre of gravity

Answer 21

when all the mass of an object is said to concentrated at one point

Question 22

lamina

Answer 22

flat 2D shape

Question 23

equation linking resultant force and momentum

Answer 23

change in momentum/time = resultant force

Question 24

what is the principle of conservation of momentum

Answer 24

momentum is always conserved in an explosion/collision, so there is no net change in momentum
momentum before = momentum after (provided there are no external forces)

Question 25

the time taken for the change in momentum to occur is proportional to the..

Answer 25

resultant force felt by the object

Question 26

reaction force

Answer 26

the upwards force from a surface in opposition to an objects weight

Question 27

energy

Answer 27

the ability to do work

Question 28

pressure in fluids formula

Answer 28

density x gravitational field strength x height

Question 29

why when moving in a cicrular horizontal path the resultant force points towards the center of the circle?

Answer 29

centripetial force (force/acceleration towards centre of circle)

Question 30

acceleration formula

Answer 30

change in velocity/time

Question 31

newtons 1st law

Answer 31

object either remains at rest or continues in a straight line at constant speed unless acted on by a resultant force

Question 32

spring constant formula

Answer 32

k = F/x

Question 33

limit of proportionality

Answer 33

the extension that Hooke's law no longer applies to - the extension is no longer proportional to the force

Question 34

describe an object in circular motion

Answer 34

1. speed increases as force increases, with mass and radius constant 2. radius decreases if force increases, with mass and speed constant 3. an increased mass requires an increased force to maintain radius and speed

Question 35

5 examples of energy stores

Answer 35

kinetic, GPE, chemical, elastic, electrostatic

Question 36

kinetic energy formula

Answer 36

1/2mv^2

Question 37

GPE formula

Answer 37

mgh

Question 38

mechanical work done

Answer 38

the amount of force needed to move an object a certain distance

Question 39

mechanical work done formula

Answer 39

W = fd

Question 40

efficiency formula

Answer 40

useful energy ouput/total energy input x 100 or useful power onput/total power input x 100

Question 41

pressure

Answer 41

force per unit area, P = F/a

Question 42

Man made things that use moments

Answer 42

Crowbar, wrench, door, tap, spanner, scissors