How Long Will It Take for a Car to Catch Up to a Truck If Both Are Moving?

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A car traveling at 115 km/h is 150 meters behind a truck moving at 75 km/h. The initial calculation attempted to find the time it takes for the car to catch up using the equation 115x = 75x + 0.15, but the result was incorrectly calculated as 0.00375 seconds. The error lies in the unit conversion and the incorrect application of the formula. To solve the problem correctly, one must ensure that the units for velocity and distance are consistent, particularly converting the speeds into meters per second or the distance into kilometers properly. The correct approach will yield the accurate time for the car to reach the truck.
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A car traveling 115 km/h is 150 m behind a truck traveling 75 km/h. How long will it take the car to reach the truck?

Ok I think I am doing this right but I can't get it to tell me I'm correct on the online homework. See what you think about what I'm doing:

150m= .15km

so then, 115x=75x+.15

which yields x= .15 / 40 = .00375 s

Is this not right? It says I am incorrect. Is there some procedure I am leaving out?
 
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Hi wadesweatt,

wadesweatt said:
A car traveling 115 km/h is 150 m behind a truck traveling 75 km/h. How long will it take the car to reach the truck?

Ok I think I am doing this right but I can't get it to tell me I'm correct on the online homework. See what you think about what I'm doing:

150m= .15km

so then, 115x=75x+.15

which yields x= .15 / 40 = .00375 s

The unit for this answer is incorrect. Look at what units the velocities have, and then you'll need to convert this answer to seconds (if that's what is asked for).
 
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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}...
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