A car heading north collides at an intersection with a truck of the same mass as the car heading east. If they lock together and travel at 28 m/s at 37° north of east just after the collision, how fast was the car initially traveling? Assume that any other unbalanced forces are negligible.
what is the correct answer
34 m/s
17 m/s
26 m/s
68 m/s

Question

asnaseer · Answer

|dw:1324991657909:dw|
If we just look at the component of momentum in the North direction, then we get:$$\begin{align}
\text{Before collision momentum in North direction }&=m\cdot v_1\
\text{After collision momentum in North direction }&=2m\cdot 28\sin(37)\
\text{so, by preservation of momentum, we get:}\
m\cdot v_1&=2m\cdot28\sin(37)\
\therefore v_1&=2\cdot28\sin(37)=56\sin(37)\
&=33.70...\
&\approx34m/s
\end{align}$$