Amy (m=144kg) is wearing a suit made of Velcro (soft fuzzy side). The hard prick

Question

Amy (m=144kg) is wearing a suit made of Velcro (soft fuzzy side). The hard prickly side of the Velcro is glued to a 4 meter tall box of monkies (m=350 kg), which is suspended vertically using a mass less 10 meter rope. "Velcro Amy" is running along level ground at a speed of 4.2 m/s when she collides with the the stationary BFOM. Amy and the BFOM stick together and swing upward. A) How fast is the amy/BFOM system moving after the collision? B) How high above the ground do they swing? C)How much work was done on the BFOM during the collision. D) What force id doing the work in part C?

Explanation / Answer

Amy mass is,m=144kg

length of box,l=4 meter

mass of monkies m2=350 kg

Initial speed of amy=4.2m/s

Initial speed of BFOM=0 m/s

final speed is,v2 we need to find

So Vf=(m1v1+m2v2)/(m1+m2)

vf=4.2*144/(144+350)=1.224 m/s

The potential energy and the kinetic energy is same so,

1/2 mv2=mgh

0.5*v2=gh

so h=0.076 m

Work=change in kinetic energy

Work=1/2 m v2=0.5*350*1.2242=262.19 J

Initial Kinetic energy is 0 for BFOM since they are in rest. So change in kinetic energy=262 .19 J

Work done is average Impact force*distance travelled=change in kinetic energy

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