A 50 kg child running at 6.0 meter per second jumps onto a stationary 10kg sled. The sled is on a level frictionless surface.(adsbygoogle = window.adsbygoogle || []).push({});

1.FIND VELOCITY AFTER CHILD JUMPS ONTO SLED

M1V1+M2V2=(M1+M2)VF

300=60VF

VF=5 M/S

2.FIND KINETIC ENERGY of the sled with the child after she jumps onto the sled.

KE=1/2MV^2

1/2(60)(5^2)=750J

3.After a short time, the moving sled with the child aboard reaches a rough level surface that exerts a constant frictional force of 54 newtons on the sled. How much work must be done by friction to bring the sled with the child to a stop?

WFf=(Ff)(D) =54d

find d

vf^2=vi^2+2ad

0=50^2 + 2(-54/60)d

1.8d=25

25/1.8 = 13.9M

now i got

wff=54x13.9 =750J

am i correct?

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# Homework Help: Am i correct?

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