Two japanese islands are connected by a long rail tunnel thatextends horizontall

Question

Two japanese islands are connected by a long rail tunnel thatextends horizontally underwater. Imagine a communication system inwhich a small rail car with a mass of 100.0kg is launched by a typeof cannon in order to transport messages between the two islands.Assume a rail car from one end of the tunnel has a speed of4.50x102m/s, which is just large enough for a constantfrictional force of -188N to cause the car to stop at the other endof the tunnel. How long does it take for the car to travel thelength of the tunnel? What is the length of the tunnel?

Explanation / Answer

Frictional force (f) = -188N We know the formula for the frictional force (f) is                    f = ma                      = m(v - u)/t   .................... (1) Here f = -188N         m = mass ofthe rail car = 100.0 kg         u = initial speedof the car = 450m/s         v = finalspeed of the car = 0 Then substitute all these values in the eq (1) and solve forthe value of the time (t) taken. Length (S) of the distance traveled by the car is              S = (v2 - u2) / (2a) Here u = 450 m/s          v = 0          a = (v -u)/t            = (0 - 450m/s)/t Here 't' is substituted here which is calculated from the eq(1) Do all the calculation work.

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