Contact Forces
Interactions which only exist between objects which are in contact.
| Name(s) | Illustration | Label(s) | Description | Equation(s)/Questions | Links |
|---|---|---|---|---|---|
| Normal Force |  |
\(\vec{F}_{n}\) or \(\vec{n}\) | Pushing force which is perpendicular (normal) to the interface where two surfaces are in contact | Usually only as large as is needed | |
| Force of Static Friction |  |
\(\vec{f}_{s}\) | Pushing force which is parallel to the interface where two surfaces are in contact and are not moving relative to one another. In a direction to prevent the relative motion of the surfaces. | \(\left |\vec{f}_{s} \right |\leq \mu_{s}\left |\vec{n} \right |\)When is it less than and when is it equal? | PhET Ramp |
| Force of Kinetic Friction |  |
\(\vec{f}_{k}\) | Pushing force which is parallel to the interface where two surfaces are in contact and are moving (slipping) relative to one another. In a direction which opposes the relative motion of the surfaces. | \(\left |\vec{f}_{k} \right |=\mu_{k}\left |\vec{n} \right |\) | PhET Forces and Motion |
| Rolling Friction |  |
\(\vec{f}_{r}\) | Pushing force between a rolling object and a surface which impedes the motion of the rolling object across the surface. This force interaction results in the conversion of kinetic energy into thermal energy. | \(\left |\vec{f}_{r} \right |= \mu_{r}\left |\vec{n} \right |\) | |
| Tension |  |
\(\vec{T}\) | Pulling force between an object such as a string, rope, or wire and some other object | Usually only as large as is neededMassless strings? | PhET Forces and Motion |
| Spring or Elastic Force |  |
\(\vec{F}_{sp}\) | Pulling or pushing force between an elastic object such as a spring or rubber band and some other object | \(\vec{F}_{sp}=-k\vec{\Delta x}\) | PhET Masses and Springs |
| Drag |  |
\(\vec{F}_{D}\) or \(\vec{D}\) | Pushing force which impedes the motion of an object through a fluid | \(F_{D}=\frac{1}{2}CA\rho v^{2}\) | |
| Thrust |  |
\(\vec{F}_{th}\) | Pushing force between a jet or rocket engine and the fuel which is expelled by the engine. | Thrust can also describe the pushing force between a propeller and the fluid through which the propeller is rotating. | |
| Buoyant Force |  |
\(\vec{F}_{B}\) | Pushing force between a submerged or partially submerged object and the fluid which surrounds it | \({F}_{B}\)=weight of fluid displaced |
Non-Contact Forces
Interactions which can exist between objects which are not in contact.
| Name(s) | Illustration | Label(s) | Description | Equation(s) | Links |
|---|---|---|---|---|---|
| Gravitational Force or Weight |  |
\(\vec{F}_{G}\) or \(\vec{W}\) | Attractive force between two massive objects | \(F_{G}=mg\) or \(F_{G}=-\frac{Gm_{1}m_{2}}{r_{1,2}^2}\)Which equation is right? | PhET Gravity Force Lab |
| Electrostatic Force |  |
\(\vec{F}_{E}\) | Attractive or repulsive force between two charged objects | \(F_{E}=\frac{kq_{1}q_{2}}{r_{1,2}^2}\) | |
| Magnetic Force |  |
\(\vec{F}_{M}\) | Attractive or repulsive force between two magnetic objects |