A 20 metric ton train moves toward the south at 40 m/s. At what speed must it tr

ID: 1397899 • Letter: A

Question

A 20 metric ton train moves toward the south at 40 m/s. At what speed must it travel to have two

times its original momentum? A metric ton is 1000 kg.

Answer in units of m/s.

Part B

At what speed must it travel to have a momentum of 4 × 105 kg · m/s? Answer in units of m/s.

Part C

If there were a speed limit for this train as it traveled through a city, but not a weight

limit, what mass must be added to the train to slow it down to 15 m/s while at the same time keeping the momentum the same as in the second part?

Answer in units of kg.

Here ,

mass of train, m = 20000 kg

let the speed be v ,

Now,

v * m = 2 * 40 * m

v = 80 m/s

the train should move at 80 m/s to have double momentum .

momentum = speed * mass

4 *10^5 = 20000 * v

v = 20 m/s

the speed of train is 20 m/s

C)
let the added mass is m kg

(m + 20000) * 15 = 4 *10^5

m + 20000 = 26666.7

m = 6666.7 kg

6666.7 kg mass should be added to the train

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