moments

Question 1

centre of gravity

Answer 1

is the point on an object where weight appears to act
(if it’s regular it’s it’s centre)

Question 2

method for centre of gravity of an irregular object

Answer 2

suspend shape from a point
use plumb line to draw vertical line
repeat at diff point
CofG is where lines cross

Question 3

weight equation

Answer 3

mass (kg) x gravitational field strength

Question 4

moment

Answer 4

a turning force
force x perpendicular distance

Question 5

moment Nm equation

Answer 5

Force N x perpendicular distance to the pivot (m)

Question 6

principle of moments

Answer 6

in order for a lever to be in equilibrium the SUM of the clockwise moments must = the SUM of the anti-clockwise moments

Question 7

moments questions tip

Answer 7

if it says take moments about point x you pretend the pivot is that pout

Question 8

moments on a beam if load is in middle

Answer 8

if load is in the middle then
Fa + Fb = W

Question 9

moments on a beam if load is closer to one pivot

Answer 9

if load is closer to one pivot (b)
it needs to exert a greater upward force
Fa + Fb = W
Fb > Fa

Question 10

explaining moments on a beam

Answer 10

• if A is the pivot the weight is a larger distance from it so it makes a large clockwise moment
• hence the force at B needs to be larger than A to make a large enough anti clockwise moment to balance it