Question

A train starts from rest with an acceleration of 2ms. A man who is 9m behind
the train runs with uniform speed and just manages to get into the train in
10sec. The speed of the man is
1) 9ms
2) 8.7ms-
3) 4.5ms
V
10.9ms​

Answer 1

Explanation:

Train:

v0= 0m/s

a= 2m/s^2

x0= 0m

So, x(t)=t^2 (m)

Man:

v0=k

a= 0m/s^2

x0= -9m

So, x(t)=-9+v0t (m)

To find out what is the position of the train when t=10s,

x(10)=10^2=100m

Now, to find out what is the speed of the man when he gets into the train, which is also when t=10s,

100=-9+v0*10

v0=k=10,9m/s

The speed of the man has to be 10.9m/s.