Formulas And Calculations Flashcards
How do you calculate speed?
Speed (v) = distance travelled (d) / time taken (t)
v = d / t
How do you calculate acceleration?
Acceleration (a) = change in velocity / time taken (t)
Charge in velocity = final velocity (v) - initial velocity (u)
a = (v - u) / t
How do you calculate the gradient/acceleration from the line on a velocity-time graph?
- make two points on each axis, as far up and down the line as possible
- y1, y2, x1, x2
Gradient = (y2 - y1) / (x2 - x1)
How do you calculate the distance travelled from the area underneath a velocity-time graph?
1) calculate the area of the rectangle / square:
Base x Height
2) calculate the area of the triangle
1/2 x Base x Height
3) calculate the area of one graphical square
4) multiply the value of one graphical square by the total number of squares
On a standard school ticker timer set up, what amount of time does each length of tape represent and how would you work out the velocity from the length of tape?
- each length of tape represents 0.1s
- v = d (length of tape) / t (0.1s)
How do you calculate the resultant force?
Simply add the forces acting on an object together and the result is the resultant force.
For example, two forces, one 25N and one of 30N act on an object with a resultant force of 55N (25 + 30)
How do you calculate force?
Force = mass x acceleration
F = ma
How can you calculate acceleration by rearranging Newton’s famous equation?
Acceleration = force / mass
a = F / m
How do you calculate weight?
Weight (W) = mass (m) x gravitational acceleration (g)
W = mg
How do you calculate momentum?
Momentum (p) = mass (m) x velocity (v)
p = mv
How do you calculate an increase in momentum?
Increase in momentum = mv - mu
Initial momentum of an object = mu
Final momentum of an object = mv
Rearrange the following formula, and explain what needs to be constant in order to make the rearrangement possible:
F = (mv - mu) / t
F = (mv - mu) / t
F = m(v - u) / t
(v - u) / t = a
F = ma
This rearrangement is possible so long as the MASS of the object is constant
Force x time = ?
Force x time = increase in momentum
How do you calculate the moment of a force?
Moment (Nm) = force (N) x perpendicular distance from pivot (d)
Moment = F x d
A child weighs 150N and sits 2m from the middle of a see-saw…
Moment = 150N x 2m = 300Nm
If an adult weighing 600N was to sit on the other side and balance the see-saw, they would have to sit 0.5m from the fulcrum…
Moment = 600N x 0.5m = 300Nm
How would you solve this in one step?
150 x 2 = 600 x d
150 x 2 / 600 = d
= 0.5m
How do you calculate orbital speed?
Orbital speed = 2 x pi x orbital radius (r) / time period (T)
2 x pi x r / T
T = time taken for a complete orbit
What is the formula for calculating current?
I = Q / t
Or…
I = P / V
I = current in amps Q = charge in coulombs T = time in seconds P = power in watts V = voltage in volts
How do you calculate potential difference?
V = W / Q
Or
V = I x R
V = potential difference in volts W = energy transferred in joules Q = charge in coulombs I = current in amps R = resistance in Ohm's
How do you calculate charge?
Q = I x t
Q = charge in coulombs I = current in amps t = time in seconds
How do you calculate power?
P = I x V
P = power in watts I = current in amps V = voltage
How do you calculate energy?
W = V x Q
Or
W = P x t
W = energy in joules P = power in watts t = time in seconds V = potential difference Q = charge in coulombs
What equation would you use to calculate the cost of running a household appliance?
Cost in pence = power in kW x time in hours x cost per kWhr
How do you calculate the speed of a wave?
Wave speed is related to its frequency and wavelength as follows:
Wave speed (m/s) = frequency (hertz) x wavelength (metres)
What is the formula for the speed of sound?
Speed of sound = frequency x wavelength
V = f x λ
