Work Package 3

Question 1

what are gears? (non-technical)

Answer 1

gears are ‘toothed wheels’ that can mesh with each other and other components

Question 2

Why do we use gears? (4)

Answer 2

1. to transmit power through a rotating mechanical system
2. to change rotational velocities
3. to give a mechanical advantage (like a lever)
4. to translate a rotational movement to linear movement

Question 3

what is angular velocity?

Answer 3

the rate at which an object rotates.

Question 4

what is angular velocity measured in?

Answer 4

rpm - revolutions per minute

Question 5

whats the gear ratio calculation using tooth counts?

Answer 5

NL / NS
NL is the number of teeth in the large gear
NS is the number of teeth in the small gear

Question 6

what is the SI unit of measurement for angular velocity? and what is the symbol for it?

Answer 6

radians per second - rad/s

the symbol is ω, sometimes Ω called omega

Question 7

what is torque?

Answer 7

a force that causes turning and can also be referred to as a moment

Question 8

what is the calculation of a torque? and what is it measured in? (given)

Answer 8

f X r - force x radius

measured in Newton meters

Question 9

what is power? what is it measured in?

Answer 9

it is the rate at which work is performed.

measured in Nm/ sec which is also known as watts

Question 10

in a rotating system, what is the calculation for power? (given)

Answer 10

power = torque x angular velocity

Question 11

in a rotating system, what is the calculation for efficiency? (given)

Answer 11

efficiency (%) = (output power/ input power) x100

Question 12

what are three uses of cams?

Answer 12

1. transmit movement from a rotating element to linear element in a mechanical system
2. to operate mechanical devices (e.g. valves)
3. to give a mechanical advantage (e.g. a cam clamp)

Question 13

what is a cam?

Answer 13

a projecting part of a rotating wheel or shaft that strikes a follower at one or more points on its circular path. It translates motion from circular to linear.

Question 14

whats a common use of cams in automotive engines?

Answer 14

part of the camshaft that operates the inlet and exhaust valves

Question 15

what do pulley systems contain?

Answer 15

contain wheels that are interconnected with rope

Question 16

when there are more wheels and turns of rope in a pulley system what happens to the mechanical advantage?

Answer 16

the mechanical advantage is greater

Question 17

what are pulley systems sometimes assembled into?

Answer 17

a block and tackle unit

Question 18

what dictates the lift at any specific cam angle?

Answer 18

the perpendicular distance between the contact point and the centreline of the cam