Formulas

Question 1

Velocity

Answer 1

v = ∆d/∆t

Question 2

Acceleration

Answer 2

a = ∆v/∆t or
a = Net force/mass

Question 3

Net force

Answer 3

Net force = acceleration*mass

Measured in Newtons (N)

Question 4

Force of gravity

Answer 4

m*g
Gravity is acceleration not velocity
Normal force is equal in magnitude and opposite in direction

Question 5

Coefficient of friction

Answer 5

μ = F (friction)/F (normal)

Question 6

Normal Force assuming gravity is always up

Answer 6

F (normal) = m*g

Question 7

Torque

Answer 7

T = F*d
T = torque in Nm
F = force in Newtons
d = distance to the pivot point

Question 8

Law of the lever

Answer 8

When the lever is stable, Effort torque = Load torque
F (effort) * d (effort) = F (load) * d (load)
d = distance to pivot

Question 9

Mechanical Advantage

Answer 9

MA = F(load) / F(effort)
If MA > 1, there is a mechanical advantage (effort force is less than load force)
If MA < 1, there is a disadvantage, (effort force is greater than load force)

Question 10

Ideal Mechanical Advantage

Answer 10

IMA = d(effort) / d(load)
IMA > 1, effort arm > load arm
d = distance to pivot

Question 11

Work

Answer 11

W = F∆d
Calculated in Joules (J)
F is force
∆d = magnitude of displacement
Zero work is done if ∆d is 0 or if force is perpendicular to the displacement

Question 12

Negative Work

Answer 12

W = -F∆d
This is when a force acts in the opposite direction of the desired displacement
This is how work done by friction is calculated

Question 13

Work done to lift objects at a constant velocity

Answer 13

Net force = 0
Action force = force of gravity
W = F∆d

Question 14

Input and output work

Answer 14

Input: Work done to make the task happen
Output: the total work done (input + negative work)

Question 15

Electrical Resistance

Answer 15

R = V/I
R = resistance in ohms (Ω)
V = electric potential difference in volts (V)
I = electric current in amps (A)
total resistance = the sum of all resistances in a series circuit

Question 16

Kirchhoff’s current law

Answer 16

Series: I(t) = I(1) = I(2) = I(3)
Parallel: I(t) = I(1) + I(2) + I(3)

Question 17

Kirchhoff’s voltage law

Answer 17

Series: V(t) = V(1) + V(2) + V(3)
Parallel: V(t) = V(1) = V(2) = V(3)

Question 18

Gravitational potential energy

Answer 18

GPE = mgh
m = mass
g = gravity
h = height

Question 19

Kinetic energy

Answer 19

KE = 1/2mv^2
m = mass
v = velocity

Question 20

Work energy theorem

Answer 20

W = ∆E = E (final) - E (initial)

Question 21

Thermal energy

Answer 21

E = F (friction)*∆d

Question 22

Power

Answer 22

P = W/∆t = ∆E/∆t
∆E = total energy converted

Question 23

Efficiency

Answer 23

Efficiency = E (output) / E (input) = P (output) / P (input)
%efficiency = efficiency * 100