It is easy to ride on a moving train, but it is dangerous to jump off. Why? Solv

Question

It is easy to ride on a moving train, but it is dangerous to jump off. Why? Solve these following questions.

1) When someone jumps down to 3 meters in open space from a train, which runs at 20 km per hour, calculate the amount of impulse. Also, if he leaps from an apartment, which floor he leaps from would be same with the above amount of impulse?

2) Show that, through the free fall, which angle of slope would be same with the situation that he lands on the ground after the jump.


Hint: Consider the relative speed, the acceleration due to gravity, sum of vector, forces acting on the body, the point of action of vector. Especially, consider the direction of the vector(sum of the direction of vertical fall and the direction of the train) when he land the ground after the jump and analyse it geometrically.


PS. I know my English is bad. I'm already feeling sorry for you guys who read this question. Anyway, there is no exact answer. So, if you wanna set any condition to solve this problem, just do it. I hope I will get good advice from this opportunity. Thank you for all.

Explanation / Answer

1) velocity in x direction is 20km/hr

vx=20km/hr

velocity in y direction is vy

Vy ^ 2 = 2*g*3

Vy = sqrt(60)

let mass of the peson be m

net inpulse will be delta p = mVx+ MVy = m*5.56 i + m*7.75 j

magitude will be m*9.535 NSec

for this much impulse on jumping from floor

at the time of touch ing the ground Vy = 9.535

so

applying V^2 = 2as

s= v^2 / 2a = 4.546 metres

so height of the fllor he i sjumping from should be 5.456 metres

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