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Standard XII

Physics

Work Done on & by the Object

Blocks are in...

Question

Blocks are initially at rest, now blocks are pushed by a 30 N force. Find work done by contact force between 8 kg & 2 kg block on the 2 kg block. during first 4 seconds.

+144 J

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-144 J

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+72 J

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-72 J

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Solution

The correct option is A +144 J
$W = F s c o s 0 = (+ v e) F s$
$s o f b l o c k s = \frac{1}{2} . a . t^{2} = \frac{1}{2} .3 \times 4 \times 4 = 24 m$
contact force on $2 k g =$ $m . a = 2 (3)$ $= 6$
$W = F . s . c o s 0 = 6 \times 24 \times (+ 1) = + 144 J$

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Blocks are initially at rest, now blocks are pushed by a 30 N force. Find work done by contact force between 8 kg & 2 kg block on the 2 kg block. during first 4 seconds.

The correct option is A +144 JW=Fscos0=(+ve)Fs s of blocks=12.a.t2=12.3×4×4=24 m contact force on 2kg= m.a=2(3) =6 W=F.s.cos0=6×24×(+1)=+144J

The correct option is A +144 J
$W = F s c o s 0 = (+ v e) F s$
$s o f b l o c k s = \frac{1}{2} . a . t^{2} = \frac{1}{2} .3 \times 4 \times 4 = 24 m$
contact force on $2 k g =$ $m . a = 2 (3)$ $= 6$
$W = F . s . c o s 0 = 6 \times 24 \times (+ 1) = + 144 J$