Mechanical advantage

Question 1

Front

Answer 1

Back

Question 2

What is an inclined plane?

Answer 2

A sloping plank or surface used to raise heavy loads to a height.

Question 3

What is the formula for the Velocity Ratio of an inclined plane?

Answer 3

VR = 1 / sin(θ) where θ is the angle of the plane with the horizontal.

Question 4

In the absence of friction how does Mechanical Advantage compare to Velocity Ratio for an inclined plane?

Answer 4

MA = VR

Question 5

What effect does friction have on the Mechanical Advantage of an inclined plane?

Answer 5

Friction reduces the Mechanical Advantage so it becomes less than the Velocity Ratio.

Question 6

Describe how an inclined plane can be used to determine the coefficient of static friction between two surfaces.

Answer 6

Increase the angle of the plane until the block just starts to slide down. The coefficient of static friction is equal to the tangent of that angle.

Question 7

Front

Answer 7

Back

Question 8

What is a pulley system?

Answer 8

A system that uses a rope passing around a wheel to lift or move loads.

Question 9

Where are pulleys often used?

Answer 9

Construction sites to raise or lower heavy loads.

Question 10

In a simple pulley system if the weight of the rope and friction are negligible how does the effort relate to the load?

Answer 10

The effort applied to the rope will be equal to the load lifted.

Question 11

What is the mechanical advantage of a simple pulley system with no friction?

Answer 11

1

Question 12

What is the velocity ratio of a simple pulley system?

Answer 12

1

Question 13

What is a block and tackle pulley system?

Answer 13

A system in which one or more pulleys are mounted on the same axle with a continuous rope passing around the pulleys.

Question 14

How is the Velocity Ratio of a pulley system calculated?

Answer 14

It is generally equal to the number of pulleys in the system.

Question 15

Does Mechanical Advantage increase or decrease as the number of pulleys increases in a pulley system?

Answer 15

Increases

Question 16

If the efficiency of a pulley system is 100% how does the Mechanical Advantage compare to the Velocity Ratio?

Answer 16

They are equal.

Question 17

Why is the efficiency of a pulley system always less than 100% in practice?

Answer 17

Due to friction and the weight of the pulleys.

Question 18

Does efficiency increase or decrease as the number of pulleys increases in a pulley system?

Answer 18

Decreases

Question 19

For a pulley system how does efficiency relate to the load to be lifted?

Answer 19

The greater the load the greater the efficiency.

Question 20

Front

Answer 20

Back

Question 21

What is a lever?

Answer 21

A stiff bar or rigid rod supported at the fulcrum or pivot about which it can rotate used to overcome a large resistance by applying a small force.

Question 22

What is the principle of moments for a lever?

Answer 22

Effort x distance of effort from fulcrum = Load x distance of load from fulcrum

Question 23

What is the formula relating Load Effort and distances from the fulcrum?

Answer 23

E x a = L x b

Question 24

How many classes of levers are there?

Answer 24

Three

Question 25

What is a first-order lever?

Answer 25

The fulcrum is between the load and the effort.

Question 26

Give examples of first-order levers.

Answer 26

Crowbar

Question 27

What is a second-order lever?

Answer 27

The load is between the effort and the fulcrum.

Question 28

Give examples of second-order levers.

Answer 28

Wheelbarrow

Question 29

What is a third-order lever?

Answer 29

The effort is between the load and the fulcrum.

Question 30

Give examples of third-order levers.

Answer 30

Forceps

Question 31

For a first-order lever what is the typical range of values for the Velocity Ratio?

Answer 31

Usually greater than 1 but could be less than or equal to 1.

Question 32

For a second-order lever what is the typical range of values for the Mechanical Advantage and Velocity Ratio?

Answer 32

Always greater than 1.

Question 33

For a third-order lever what is the typical range of values for the Mechanical Advantage and Velocity Ratio?

Answer 33

Less than 1.

Question 34

Front

Answer 34

Back

Question 35

Define a machine.

Answer 35

A device or tool which allows a force (or effort) applied at one point to overcome a resisting force (or load) at another point.

Question 36

What is the purpose of a machine?

Answer 36

To enable us to overcome a large resistance or load by applying a small effort and to do work more easily and conveniently.

Question 37

Give examples of simple machines.

Answer 37

Lever

Question 38

Define Effort.

Answer 38

The force applied to a machine.

Question 39

Define Load.

Answer 39

The force or resistance overcome by the machine.

Question 40

Define Mechanical Advantage (MA) or Force Ratio (FR).

Answer 40

The ability of a machine to overcome a large load through a small effort.

Question 41

What is the formula for Mechanical Advantage?

Answer 41

MA = Load / Effort

Question 42

Define Velocity Ratio (VR).

Answer 42

The ratio of the distance moved by the effort to the distance moved by the load in the same time interval.

Question 43

What is the formula for Velocity Ratio?

Answer 43

VR = distance moved by effort / distance moved by load

Question 44

For an ideal or perfect machine how does Mechanical Advantage compare to Velocity Ratio?

Answer 44

Mechanical Advantage = Velocity Ratio

Question 45

Define Efficiency of a machine.

Answer 45

The ratio of the useful work done by the machine to the work put into the machine usually expressed as a percentage.

Question 46

What is the formula for Efficiency?

Answer 46

Efficiency = (Useful work done by the machine / Work put into the machine) x 100%

Question 47

Why is the efficiency of a practical machine usually less than 100%?

Answer 47

Because of friction in the moving parts of the machine.

Question 48

Front

Answer 48

Back

Question 49

What is a conservative force?

Answer 49

A force where the work done by it on a particle moving between two positions depends only on the initial and final positions and is independent of the path taken.

Question 50

Give examples of conservative forces.

Answer 50

Gravitational force and elastic force.

Question 51

What is the principle of conservation of mechanical energy?

Answer 51

In a closed or isolated system the total mechanical energy is always conserved although energy may change from one form to another.

Question 52

What is an example of a non-conservative force?

Answer 52

Friction.

Question 53

What happens to mechanical energy when friction is present?

Answer 53

Some mechanical energy is lost and reappears as heat.

Question 54

State the general principle of the conservation of energy.

Answer 54

The total energy in a given system is always constant or energy can neither be created nor destroyed although it can be transformed from one form to another.

Question 55

In a swinging pendulum how is mechanical energy conserved?

Answer 55

The total energy is continuously changing between kinetic and potential

Question 56

Front

Answer 56

Back

Question 57

What is the definition of work?

Answer 57

Work is said to be done whenever a force moves its point of application a distance in the direction of the force.

Question 58

What is the formula for work when the force is at an angle?

Answer 58

W = F cos(θ) x S

Question 59

What are the two types of mechanical energy?

Answer 59

Potential energy and kinetic energy.

Question 60

Define potential energy.

Answer 60

Potential energy is the energy possessed by a body by virtue of its position or state or configuration.

Question 61

Give an example of elastic potential energy.

Answer 61

A wound-up clock spring.

Question 62

What is the formula for elastic potential energy?

Answer 62

E_p(elastic) = 1/2 kx^2

Question 63

Define gravitational potential energy.

Answer 63

Energy possessed by a body when it is raised a certain height against the force of gravity.

Question 64

What is the formula for gravitational potential energy?

Answer 64

E_g = mgh

Question 65

Define kinetic energy.

Answer 65

The energy or capacity to do work possessed by a body because of its motion.

Question 66

What is the formula for kinetic energy?

Answer 66

K.E. = 1/2 mu^2