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At a particular instant velocity and acc...

At a particular instant velocity and acceleration of a particle are `(-hat(i)+hat(j)+2hat(k))m//s` and `(3hat(i)-hat(j)+hat(k))m//s^(2)` respectively at the given instant particle's speed is `:`

A

increasing

B

decreasing

C

constant

D

can't be say

Text Solution

Verified by Experts

The correct Answer is:
B
`vec(v)=-hat(i)+hat(j)+2hat(k)`
`vec(a)=3hat(i)-hat(j)+hat(k)`
`vec(a).vec(v)=-3-1+2lt0`
hence, `theta gt90^(@)` between `vec(a)` and `vec(v)`
so speed is decreasing
`vec(a).vec(v)=-3-1+2lt0`
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