Simple Machine

Machine

Machine is any device by means of which a force applied at one point can be used to overcome a force at a different point

Simple Machine

The applied force is called Effort

The force which effort overcomes is called Load (The force which an object pulls or pushes on a machine is called Load.)

Types of simple machine

Types of simple machine

Mechanical Advantage (M.A.)

The mechanical advantage of a machine is defined as the ratio of the load to the effort.

Formula for mechanical advantage

M.A = load Effort

Velocity Ratio (V.R.)

The velocity ratio of a machine is defined as the ratio of the distance moved by effort to the distance moved by the load in the same time.

Formula for Velocity Ratio (V.R.)

V.R = distance moved by effort(dE) distance moved by load in the same time(dL)

Efficiency

The efficiency of a machine is defined as the ratio of the useful work done by the machine to the total work put into the machine.

Formula for Efficiency

Efficiency = M.A V.R × 100%

Example 1

Calculate the mechanical advantage of the diagrams below.

1.

mechanical advantage  example 1

Solution

M.A = load Effort

given that

Load = 100N

Effort = 20N

M.A = ?

M.A = 100 20

Answer: M.A = 5

2.

mechanical advantage  example 2

Solution

M.A = load Effort

given that

Load = 30N

Effort = 15N

M.A = ?

M.A = 30 15

Answer: M.A = 2

3.

mechanical advantage  example 3

Solution

M.A = load Effort

given that

Load = 35N

Effort = 5N

M.A = ?

M.A = 35 5

Answer: M.A = 7

Example 2

Calculate the velocity ratio of the diagrams below.

1.

mechanical advantage  example 4

Solution

V.R = distance moved by effort(dE) distance moved by load in the same time(dL)

Given that

dE = 1m

dL = 50cm

V.R = ?

First convert 50cm to metres(m)

dL = 0.5m

V.R = 1 0.5

Answer: V.R = 2

Example 3

The diagram below shows a pulley system. An effort of 1000N is required to raise a load of 4500N.

mechanical advantage  example 5

(a) Find the mechanical advantage.

(b) Find the velocity ratio.

(c) Find the efficiency.

Solution

(a)

M.A = load Effort

Given that

M.A = ?

load = 4500N

Effort = 1000N

M.A = 4500 1000

Answer: M.A = 4.5

(b)

To find the velocity ratio of the pulley system, count the number of lines connected to moving pulley.

Therefore 6 lines connected to moving pulleys.

Answer: V.R. = 6

(c)

Efficiency = M.A V.R × 100%

Efficiency = ?

M.A = 4.5

V.R = 6

Efficiency = 4.5 6 × 100%

Answer: Efficiency = 75%