Chapter 7: Work, Energy, and Simple Machines

Vocabulary flashcards covering the key terms, definitions, laws, and simple machines from Chapter 7: Work, Energy, and Simple Machines.

Work Done by a Constant Force

The product of the applied force and the displacement in the direction of the force, mathematically represented as $W = F \times s$.

Joule ($\text{J}$)

The SI unit of work and energy, defined as the work done when a constant force of $1\,\text{N}$ displaces an object by $1\,\text{m}$ in the direction of the force ($1\,\text{J} = 1\,\text{N} \times 1\,\text{m} = 1\,\text{kg}\,\text{m}^2\,\text{s}^{-2}$).

Positive Work

Work done on an object when its displacement is in the same direction as the applied force.

Negative Work

Work done on an object when its displacement is in the opposite direction to that of the applied force.

Zero Work

The condition where the work done by a force on an object is zero, occurring when the force is zero ($F = 0$), the displacement is zero ($s = 0$), or the force acts perpendicular to the direction of displacement.

Work-Energy Theorem

A fundamental theorem stating that the work done on an object or system is equal to the change in its energy ($\text{work done on an object} = \text{change in its energy}$).

James Prescott Joule

The scientist after whom the SI unit of work and energy is named; he investigated how mechanical energy and thermal energy relate and convert into each other.

Mechanical Energy

The form of energy that an object possesses due to its motion or its position, defined as the sum of its kinetic energy and potential energy.

Kinetic Energy

The energy possessed by an object by virtue of its motion, given by the expression $K = \frac{1}{2}mv^2$.

Potential Energy

The energy stored by an object as a result of its deformation or stored in a system of objects due to their relative positions.

Gravitational Potential Energy

The potential energy of an object of mass $m$ raised to a height $h$ near the Earth's surface against gravity, expressed as $U = mgh$.

Conservation of Mechanical Energy

The principle stating that as an object moves under the influence of gravity alone, its total mechanical energy remains constant if no other external forces act upon it.

Power

The physical quantity defined as the rate at which work is done, calculated as work done divided by the time taken ($P = \frac{W}{t}$).

Watt ($\text{W}$)

The SI unit of power, named after James Watt, equal to $1\,\text{joule}$ of work done per second ($1\,\text{W} = 1\,\text{J}\,\text{s}^{-1}$).

Horsepower (hp)

A common unit of power used primarily for car engines and water pumps, where $1\,\text{horsepower} = 746\,\text{W}$.

Simple Machines

Devices that make tasks easier by altering the magnitude or direction of the applied force without changing the total work required.

Effort

The force applied by an external agency to a simple machine to perform a task.

Load

The resisting force or weight that needs to be overcome or moved by a machine.

Mechanical Advantage

The quantitative ratio of the load to the effort in a machine, given by $\text{mechanical advantage} = \frac{\text{load}}{\text{effort}}$.

Fixed Pulley

A wheel with a groove guiding a rope fixed at the top, which provides convenience by changing the direction of the effort and possesses a mechanical advantage of $1$.

Inclined Plane

A sloping surface that acts as a simple machine with a mechanical advantage of $\frac{L}{h}$, enabling a heavy load to be raised to a height $h$ over a ramp length $L$ using a smaller effort force over a longer distance.

Lever

A simple machine comprising a rigid bar that rotates about a fixed point called a fulcrum.

Fulcrum

The fixed pivot point about which a lever rotates.

Effort Arm

The perpendicular distance from the fulcrum to the point on the lever where the effort force is applied.

Load Arm

The perpendicular distance from the fulcrum to the point on the lever where the load is positioned.

Class I Lever

A class of lever in which the fulcrum is situated between the load and the effort (examples include seesaws, scissors, crowbars, pliers, and beam balances).

Class II Lever

A class of lever in which the load is situated between the fulcrum and the effort (examples include lemon squeezers, wheelbarrows, and bottle openers).

Class III Lever

A class of lever in which the effort is applied between the fulcrum and the load (examples include tongs, tweezers, brooms, hammers, and oars).

Gharat (Panchakki)

A traditional water mill in the Himalayan region that converts the gravitational potential energy of downhill flowing water into kinetic energy to turn a grinding stone and grind grain.

Dark Energy

A hypothesized form of energy proposed by scientists to explain why the expansion of the Universe is accelerating.