UNIT E: Mechanical Systems

Question 1

What is the formula for work?

Answer 1

force x distance

Question 2

What is the formula for speed ratio?

Answer 2

load force / effort force
effort arm / load arm

Question 3

What are the formulas for mechanical advantage? Are there units?

Answer 3

driver teeth / # driven teeth
No units

Question 4

What are the formulas for efficiency?

Answer 4

output force / input force x 100
MA / SR x 100

Question 5

What is the formula for pressure? What are the units?

Answer 5

force / area
UNITS: f - N, A - m2, P - Pa or N/m2

Question 6

What is a machine? Give an example.

Answer 6

Any device that helps to do work. i.e. hairbrush

Question 7

What’s the difference between systems and subsystems?

Answer 7

Subsystem - a system of its own i.e. wheel and axle
System - subsystems put together

Question 8

Give 3 examples of energy sources for machines.

Answer 8

Human force, wind, fossil fuels.

Question 9

How do gears transfer energy?

Answer 9

The teeth mesh together and transfer energy through rotation.

Question 10

What is the difference between potential and kinetic energy?

Answer 10

Potential: stored energy
Kinetic: energy in motion

Question 11

What is efficiency?

Answer 11

A measure of how well a machine uses energy.
More energy being lost = less efficient

Question 12

The work done by a ramp is 1350J, and the work done by the effort force is 2134J. What is the efficiency of the machine?

Answer 12

1350/2134 x 100 = 63.26%

Question 13

What si friction? How do you reduce it?

Answer 13

Force applied in opposite direction; a resistant force.
Can be reduced with oil/grease

Question 14

What are the 6 types of simple machines?

Answer 14

Lever
Inclined plane
Wedge
Screw
Pulley
Wheel & axle

Question 15

What is mechanical advantage?

Answer 15

Comparison of force produced by machine and force applied to machine

Question 16

How are pulleys and levers alike?

Answer 16

Both lift objects, use a rotational movement.

Question 17

Describe fluid pressure.

Answer 17

the force per unit area on a specific item on the surface of a closed container.

Question 18

How are forces transmitted in all directions?

Answer 18

Pascal’s law says pressure applied to an enclosed fluid is transmitted equally.

Question 19

How does hydraulic pressure create MA?

Answer 19

allows to use a small force on a small piston to produce a larger force on the large piston.

Question 20

Does shape have effect on pressure?

Answer 20

No

Question 21

Can machines be 100% efficient? Why or why not?

Answer 21

They cannot, work is always lost through friction and heat