12 Power, Work & Energy
Resources
- Extra Help: A-Level Physics Tutor
- Article to Read: Bye Aerospace’s Sun Flyer 2 completes first flight with Siemens electric propulsion motor
Equations Introduced and Used for this Topic:
- [latex]a = \dfrac{\Delta v}{t}[/latex]
- [latex]\Delta v = v_f - v_i[/latex]
- [latex]v_f = v_i + a t[/latex]
- [latex]d = v_i t + \frac{1}{2} a t^2[/latex]
- [latex]F = m a[/latex]
- Work [latex](W) = F \cdot d[/latex] or [latex]F d \cos ø[/latex]
- [latex]E_p = m g h[/latex]
- Power [latex](P) = \dfrac{W}{t} = \dfrac{\Delta \text{ Energy}}{t}[/latex]
- [latex]P = \frac{1}{2}\varrho A v^3[/latex]
- [latex]\vec{a} = \dfrac{\vec{\Delta v}}{t}[/latex]
- [latex]v = \dfrac{(v_i + v_f)}{2}[/latex]
- [latex]2 a d = v_f^2 - v_i^2[/latex]
- [latex]d = \dfrac{(v+i v_f) t}{2}[/latex]
- [latex]w = m g[/latex]
- [latex]W = \Delta \text{ Energy}[/latex]
- [latex]V[/latex] or [latex]V_g = g h[/latex]
- [latex]E_k = \frac{1}{2} m v^2[/latex]
- [latex]\text{Efficiency } = \text{ Output } \times 100%[/latex]
| Equations | a | vt | vi | d | t |
|---|---|---|---|---|---|
| [latex]v_t = v_i + at[/latex] | Not mentioned | ||||
| [latex]2ad = v_{r}^{2} - v_{i}^{2}[/latex] | Not mentioned | ||||
| [latex]d = v_{i}t + \dfrac{1}{2} at^2[/latex] | Not mentioned | ||||
| [latex]d = \dfrac{(v_i + v_t)t}{2}[/latex] | Not mentioned |
Where…
- [latex]P[/latex] is the power, measured in watts (W)
- [latex]W[/latex] is work, measured in joules (J)
- [latex]\varrho[/latex] is the density of the moving medium, measured in kilograms per metre cubed (kg/m3)
- [latex]A[/latex] is the cross sectional area of the turbine, measured in metres squared (m2)
- [latex]v[/latex] is the speed of the medium moving through the turbine, measured in metres per second (m/s)
- [latex]v[/latex] is the speed of the object commonly measured in metres/second (m/s) or kilometres/hour (km/h)
- [latex]\Delta \text{ Energy}[/latex] is the change in energy and can be any form of energy ([latex]E_p[/latex] or other forms), measured in joules (J)
- [latex]E_p[/latex] is gravitational potential energy, measured in joules (J)
- [latex]E_k[/latex] is kinetic energy, measured in joules (J)
- [latex]V[/latex] or [latex]V_g[/latex] is the gravitational potential, measured in newtons per kilogram (N/kg)
- [latex]\Delta h[/latex] is the change in vertical height, measured in metres (m)
- [latex]F[/latex] is force, measured in newtons (N)
- [latex]m[/latex] is mass, commonly measured in kilograms (Kg), grams (g) or tonnes (t)
- [latex]g[/latex] or [latex]a_g[/latex] is the acceleration due to gravity and varies from 9.78 m/s2 (equator) to 9.83 m/s2 (North or South poles)… The average value of gravity is taken to be either 9.80 m/s2 or 9.81 m/s2
- [latex]\vec{v}[/latex] is velocity, commonly measured in metres/second (m/s) or kilometres/hour (km/h) and includes a direction
- [latex]v_i[/latex] is initial speed, commonly measured in metres/second (m/s) or kilometres/hour (km/h)
- [latex]\vec{v_i}[/