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A force (2hat I + hat j - hat k)N acts ...

A force ` (2hat I + hat j - hat k)N` acts on a body which is initially at rest. At the end of 20 sec the velocity of the body is `(4 hat i + 2 hat j – 2 hat k) ms^(-1)`,then mass of the body is

A

(a) 8 kg

B

(b)10 kg

C

(c )5 kg

D

(d) 4.5 kg

Text Solution

Verified by Experts

The correct Answer is:
(b)
velocity,`V = F/(M)t`
`rArr V = sqrt((4)^(2)+(2)^(2)+(2)^(2) = sqrt24`
`rArr F = sqrt(2)^(2)+1^(2)+1^(2) = sqrt(6)`
` rArr sqrt24 = sqrt 6 xx 20/(M)`
`:. M = sqrt(6)xx20/(sqrt(24))=20/(2)=10 kg`
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