Finding Distance b/w Point A and B with Kinematic Formulas

  • Thread starter Thread starter lektor
  • Start date Start date
  • Tags Tags
    Mechanics
AI Thread Summary
The discussion focuses on calculating the distance between two cars moving toward each other with given speeds and accelerations. The initial approach involved using kinematic formulas, but there were concerns about the resulting units being inconsistent. A proposed formula for distance, D, was shared, which incorporates the initial velocities and accelerations of both cars. Participants discussed deriving the formula by expressing the positions of the cars as functions of time and solving a quadratic equation. The conversation emphasizes the importance of ensuring unit consistency in the final result.
lektor
Messages
56
Reaction score
0
This question is just a practice for creating equations for suiting situations but i feel as if I've taken the completely wrong appoach..


Two cars begin to move toward each other simultaneously along a straight road. Car 1 starts from point A at a speed of V1; Car 2 starts at point B at a speed V2.The acceleration of car 1 is a1; it is directed toward A,
The acceleration of car 2 is a2; it is directed toward B. In the process of motion, the cars meet twice; the time interval between the meetings is t. Find the distance between A and B.

Some help would be great, so far my approach was using kinematic formulas.

I finished with D = \sqrt{\frac{Vi1*T*a1*T^2}{Vi2*T*a2*T} }

Sorry about the mathlatex in currently reading the guide.
 
Last edited:
Physics news on Phys.org
The units in your result don't agree. They are ms, and not m.

I came up with this formula:


D = \frac{(v_{01} + v_{02})^2 - (\frac{a_1 + a_2}{2\Delta t})^2}{2(a_1 + a_2)}
 
ramollari said:
The units in your result don't agree. They are ms, and not m.

I came up with this formula:


D = \frac{(v_{01} + v_{02})^2 - (\frac{a_1 + a_2}{2\Delta t})^2}{2(a_1 + a_2)}

Your Answer looks quite well thought out, could you please give some explanations of how you reached it :)?
 
Express the positions x of both vehicles in terms of time. Equalize them, and you get a quadratic equation for time, that of course gives two results. Then, the procedure is simple:

\Delta t = \frac{\sqrt{\Delta}}{a}

Both Delta and a will contain the quantities D, a1, a2, v01, v02. So, solve for D to arrive at that result.
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
Back
Top