#1: Two children with masses of 22 and 32 kg are sitting on a balanced seesaw. I
ID: 1280494 • Letter: #
Question
#1: Two children with masses of 22 and 32 kg are sitting on a balanced seesaw. If the lighter child is sitting 3 m from the center, where is the heavier child sitting?
#2: A planet follows an elliptical orbit that brings it as close as 21 million km to a star and as far as 90 million km from the star. At both of these locations the velocity of the planet makes a right angle to the direction to the star. If the planet's speed is 38 km/s when it is farthest from the star, how fast is it moving when it is closest to the star?
#3: A child with a mass of 18 kg sits at a distance of 2 m from the pivot point of a seesaw. Where should a 15 kg child sit to balance the seesaw?
#4: A child with a mass of 48 kg is riding on a merry-go-round. If the child has a speed of 3 m/s and is located 2.5 m from the center of the merry-go-round, what is the child's angular momentum?
Explanation / Answer
1) balance the torque 22*3=32*x
x=2.0625m
2) apply conservation of angular momentum
m*v1*r1=m*v2*r2
where 1 and 2 are location indices
v1*r1=v2*r2
90*38=21*v
v=162.85 km/sec
3) balance torque agan
18*2=15*x
x=2.4 m
4) angukar momentum= m*v*r
=48*2.5*3
=360 kg.m^2/sec
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