# p2.3 (2) Flashcards Preview

## OCR GCSE P1-P5 > p2.3 (2) > Flashcards

Flashcards in p2.3 (2) Deck (24)
1
Q

what is needed for an object to rotate?

A

a pivot, a force

2
Q

define a moment

A

the measure of its turning effect, about a pivot

3
Q

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

A

increase the perpendicular distance from the pivot

4
Q

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

A

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

5
Q

are moments scalar or vector?

A

a vector (either anticlockwise or clockwise)

6
Q

where would the principle of moments be present?

A

on a see-saw

where any body is in equilibrium

7
Q

what happens when the principle of moments holds true?

A

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

8
Q

equation to see an object is in equilibrium (moments)

A

sum of anticlockwise moments = sum of clockwise moments

9
Q

what is a key concept to remember when calculating moments?

A

must take into account PERPENDICULAR distance from pivot

10
Q

explain what a lever does

A
• 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

11
Q

A

a measure of force amplification achieved by a tool

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

12
Q

equation to calculate mechanical advantage (of a lever)?

A

MALE

effort

13
Q

explain how a gear acts

A
• as a moment multiplier
14
Q

how do gears multiply moments?

A

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

FORCE STAYS SAME

15
Q

equation to calculate mechanical advantage (of a gear)?

A

OI

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

16
Q

how do gears transmit forces?

A
• 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
17
Q

at what angle do pressures exert forces to any surface?

A

right angles

18
Q

what is the equation to calculate pressure?

A

area (m^2)

19
Q

what is the unit for pressure?

A

pascals (Pa)

20
Q

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

A

equally, directions

21
Q

define a hydraulic machine

A

a force multiplier that uses a liquid to transmit a force

22
Q

does the pressure change within a hydraulic machine?

A

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

23
Q

how do hydraulic brakes act as a force multiplier?

A

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

24
Q

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

A

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

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