Chapter 7 Work & Simple Machines

Question 1

Mechanical work (W)

Answer 1

when a force acts on an object to move it parallel to the force vector.

Question 2

Formula for mechanical work

Answer 2

W = F x d (Work in joules is Force in newtons x displacement in meters)

Question 3

Work is what type of quantity? (scalar or vector?)

Answer 3

scalar (it can be positive, negative, or zero)

Question 4

A book has what kind of energy after it is raised?

Answer 4

gravitational potential energy

Question 5

A larger motor delivers more ___ to move the vehicle than a smaller motor.

Answer 5

force

Question 6

Power (P) is the rate of doing ___?

Answer 6

work

Question 7

Formula to computer mechanical power

Answer 7

P = Work / change in time (time interval)

Question 8

Watt (W)

Answer 8

the unit of power in the SI

One watt is 1 J of work done in 1 s

Question 9

Simple machines

Answer 9

tools, composed of basic mechanical parts, that cannot create their own energy

Question 10

formula for efficiency

Answer 10

efficiency = W out / W in x 100%

Question 11

What is the “load” or “resistance”?

Answer 11

the system to be moved (by a machine)

Question 12

The force you exert on the simple machine

Answer 12

The effort force [ F(e)]

Question 13

The force that the load exerts on the machine

Answer 13

the resistance force [ F(r)]

Question 14

Lever

Answer 14

a rigid bar that rests on a pivot point called a fulcrum (like your Revolution board)

Question 15

Torque

Answer 15

the product of a force and the distance from the pivot point.

Question 16

Law of Torques

Answer 16

formula that applies to lever systems in rotational equilibrium (w(1) x l(1) = w(2) x l(2)

Question 17

Three types of levers

Answer 17

1st Class (with the fulcrum between the resistance and effort points like a seesaw), 2nd Class (with the fulcrum at one end and effort at the other like wheelbarrow), and 3rd Class (fulcrum at one end and resistance at the other end like arm/hand).

Question 18

When a lever doesn’t have equilibrium, what occurs?

Answer 18

acceleration and motion

Question 19

Rotational motion

Answer 19

movement of an object about a central axis or pivot point

Question 20

a wheel

Answer 20

any rotating object that has a force applied to it at some distance from the center axis (creating torque).

Question 21

gear

Answer 21

a modified wheel and axle with “teeth” around its circumference that mesh with another gear

Question 22

two types of gears

Answer 22

effort gear and resistance gear