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A 120 g mass has a velocity vecv=2hati+5...

A 120 g mass has a velocity `vecv=2hati+5hatj m s^(-1)` at a certain instant. Its kinetic energy is

A

3 J

B

4 J

C

5 J

D

1.74 J

Text Solution

Verified by Experts

The correct Answer is:
D
Here, m=120 g = `120 xx 10^(-3)` kg = 0.12 kg
`vecv=2hati+5hatj m s^(-1)`
`therefore v^2=vecv.vecv=(2hati+5hatj).(2hati+5hatj)=4+25=29 m^2 s^(-2)`
Kinetic energy, `K=1/2 m.v^2`
`=1/2 xx 0.12 kg xx (29 m^2 s^(-2)) =1.74 J`
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Knowledge Check

  • A 300 g mass has a velocity of (3hati + 4hatj) m//s at a certain instant what is its K.E. ?

    A
    1.35 J
    B
    2.4 J
    C
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    D
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    A
    `2.3 m s^(-1)`
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    C
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    D
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