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--- 183_notes:examples:netforce [2014/07/10 17:06] – [Solution] caballero
+++ 183_notes:examples:netforce [2017/12/05 02:48] (current) – pwirving
@@ Line 2: / Line 2: @@
 ====== Example: Calculating the net force ======
-The fan cart in the video below is observed to experience a net force to the right. Determine the (vector) net force acting on the fan cart.
+The fan cart is observed to experience a net force to the right.
+Determine the (vector) net force acting on the fan cart.
 ==== Setup ====
@@ Line 38: / Line 39: @@
 We simply compute the force vector noting that the momentum does not change in the vertical direction, so the forces on the cart due to gravity and the force on the cart due to the track are equal in magnitude.
-The force on the cart due to the Earth is given by $F_{Earth} = m\vec{g}$ where $\vec{g} = \langle 0, -9.8, 0 \rangle$ \dfrac{m}{s^2}$. We compute,
+The force on the cart due to the Earth is given by $F_{Earth} = m\vec{g}$ where $\vec{g} = \langle 0, -9.8, 0 \rangle \dfrac{m}{s^2}$. We compute,
-$$F_{Earth} = m_{cart}\vec{g} = 0.3 kg \langle 0, -9.8, 0 \rangle \dfrac{m}{s^2} = \langle 0, -2.94, 0 \rangle N$$
+$$F_{Earth} = m_{cart}\vec{g} = 0.3 kg\:\langle 0, -9.8, 0 \rangle \dfrac{m}{s^2} = \langle 0, -2.94, 0 \rangle N$$
 So, we can now compute the net force,
-$$\vec{F}_{net} = \sum \vec{F}_i  = \vec{F}_fan + \vec{F}_{Earth} + \vec{F}_{track} = \langle 0.45, 0, 0 \rangle N + \langle 0, -2.94, 0 \rangle + \langle 0, 2.94, 0 \rangle = \langle 0.45, 0, 0 \rangle N$$
+$$\vec{F}_{net} = \sum \vec{F}_i  = \vec{F}_{fan} + \vec{F}_{Earth} + \vec{F}_{track} = \langle 0.45, 0, 0 \rangle N + \langle 0, -2.94, 0 \rangle + \langle 0, 2.94, 0 \rangle = \langle 0.45, 0, 0 \rangle N$$
+Notice this is simply the force that the air exerts on the blades. This is the force responsible for the momentum change of the fan cart.