p2.3 (2)

Question 1

what is needed for an object to rotate?

Answer 1

a pivot, a force

Question 2

define a moment

Answer 2

the measure of its turning effect, about a pivot

Question 3

if the force applied to the object remains constant, how would the moment increase?

Answer 3

increase the perpendicular distance from the pivot

Question 4

what is the equation to calculate the moment of an object?

Answer 4

force (N) x perpendicular distance from point to force (m)

Question 5

are moments scalar or vector?

Answer 5

a vector (either anticlockwise or clockwise)

Question 6

where would the principle of moments be present?

Answer 6

on a see-saw

where any body is in equilibrium

Question 7

what happens when the principle of moments holds true?

Answer 7

no accelerating = nothing is turning = no resultant moment acting about a point

Question 8

equation to see an object is in equilibrium (moments)

Answer 8

sum of anticlockwise moments = sum of clockwise moments

Question 9

what is a key concept to remember when calculating moments?

Answer 9

must take into account PERPENDICULAR distance from pivot

Question 10

explain what a lever does

Answer 10

• acts as a force multiplier

- so a small effort (force) can be applied to one side + a larger effort is exerted on the opposite side of the pivot

Question 11

what is mechanical advantage?

Answer 11

a measure of force amplification achieved by a tool

so a lever’s mechanical advantage must always be greater than 1

Question 12

equation to calculate mechanical advantage (of a lever)?

Answer 12

MALE

effort

Question 13

explain how a gear acts

Answer 13

• as a moment multiplier

Question 14

how do gears multiply moments?

Answer 14

as the perpendicular distance changed from the load to the pivot (radius of pivot)

FORCE STAYS SAME

Question 15

equation to calculate mechanical advantage (of a gear)?

Answer 15

OI

input cog radius

again, must be greater than 1 (is a multiplier)

Question 16

how do gears transmit forces?

Answer 16

• basically rotating levers
• small cog makes larger cog rotate with same force (passed by teeth)
• but radius is greater = a greater perpendicular distance = a greater moment

Question 17

at what angle do pressures exert forces to any surface?

Answer 17

right angles

Question 18

what is the equation to calculate pressure?

Answer 18

area (m^2)

Question 19

what is the unit for pressure?

Answer 19

pascals (Pa)

Question 20

when a force is applied to water it transmits it ………….. in all …………….

Answer 20

equally, directions

Question 21

define a hydraulic machine

Answer 21

a force multiplier that uses a liquid to transmit a force

Question 22

does the pressure change within a hydraulic machine?

Answer 22

no, the pressure applied to the master piston is equal to the slave piston (as liquids cannot be compressed)

Question 23

how do hydraulic brakes act as a force multiplier?

Answer 23

they increase the force by increasing the area of the slave piston compared to master piston

p = f/a, pressure remains constant, so a higher area means a greater force is applied

Question 24

what is the main reason why hydraulic machines can act as force multipliers?

Answer 24

as pressure is constant for fluids (exerts an equal force in all directions)

• so greater area = greater force (to keep pressure constant)