1.

Rain is falling with a velocity `(-4hat(i)+8hat(j)-10hat(k))`. A person is moving with a velocity of `(6hat(i)+8hat(j))` on the ground. Find the velocity of rain with respect to man and the direction from which the rain appears to be coming.

Answer» Correct Answer - `(-10hat(i)-10hat(k))` rain appears to come`45^(@)` with `hat(i)`
`vec(V)_(rm)=vec(V)_(r)-vec(V)_(m)=(-10hat(i)-10hat(k))`
Ans. `(-10hat(i)-10hat(k))` rain appears to come `45^(@)` with `hat (j)`
`(A)W_(CL)+W_(t)=DeltaKE :. W_(CL)=DeltaKE-W_(f)`
`(a)` During accelerated motion negative work is done against friction and there is also change is kinetic energy. Hencenetwork needed is `+ve.`
`(b)` During uniform motion work is doen against friction only and that is `+ve`.
`(c)` During retarded motion, the load has to be stopped in exactly 50 metres. If only friction is considered then then where it has to stop.
Hence the camel has to apply some force so that the load stops in `50m gt (12.5m)`.
Therefore the work done in this case is also `+ve`.


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