Work and Energy — Class 9 Maharashtra SSC Science revision notes
A 3-page visual revision sheet for Work and Energy, written for Class 9 Maharashtra SSC Science. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
Page 1 as PDF
Work and Energy in one look
work in the scientific sense, the two mechanical energies, and the rate at which energy is used
What counts as work
- work is done only when a force moves its point of application, and it is force times displacement in the direction of the force
- so W = F s cosθ, where θ is the angle between the force and the displacement
- no displacement means no work, however tiring the effort. Pushing a wall that does not move is zero work in this sense
- force perpendicular to the motion does no work, since cos 90° is zero. Carrying a bag horizontally does no work against gravity
- positive work when the force is along the motion, and negative work when it opposes, as friction does
- work is a scalar, measured in joules, and one joule is one newton acting through one metre
The relations of this chapter
- work done by a force at an angle
W = Fscosθ - kinetic energy of a moving body
K = 1/2mv^2 - potential energy at a height
U = mgh - the work energy theorem
W = K_f - K_i - power, the rate of doing work
P = W/t - and power in terms of speed
P = Fv
The two mechanical energies
- kinetic energy is the energy a body has because it is moving, and it is always positive
- potential energy is the energy a body has because of its position, usually its height
- the work energy theorem: the net work done on a body equals its change in kinetic energy
- potential energy is measured from a chosen reference level, so only differences in it are meaningful
- the path does not matter for gravitational potential energy, only the change in height
- so lifting a box straight up or carrying it up a ramp needs the same work against gravity, though friction may add more on the ramp
Page 1 of 3. The full sheet, all 3 pages, opens free in the app.
What this Work and Energy sheet covers
- Work
- Positive and negative work
- What counts as work
- The relations of this chapter
- work done by a force at an angle
- kinetic energy of a moving body
- potential energy at a height
- the work energy theorem
- power, the rate of doing work
- and power in terms of speed
- Kinetic energy
- Potential energy
- The two mechanical energies
- Law of conservation of energy
- Energy transformation
- Conservation of energy
- Using conservation of energy
- Power
- Watt
- Commercial unit of energy
- The forms energy takes
- Symbols in this chapter
- Traps that cost marks
- Tricks that save time
How CapCompass uses this sheet
These notes are not a standalone PDF. CapCompass plans Science chapter by chapter against your real exam dates and free hours, and when the plan reaches Work and Energy the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.
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