1.A 38.0 kg child swings in a swing supported by two chains, each 3.02 m long. (

Question

1.A 38.0 kg child swings in a swing supported by two chains, each 3.02 m long.

(a) If the tension in each chain at the lowest point is 342 N, find the child's speed at the lowest point.
m/s

(b) What is the force exerted by the seat on the child at the lowest point? (Neglect the mass of the seat.)
N (upward)

3.A phonograph record accelerates from rest to 26.0 rpm in 3.63 s.

(a) What is its angular acceleration in rad/s2?

Consider the known variables to determine which rotational kinematic equation should be used here. rad/s2

(b) How many revolutions does it go through in the process?
rev

1.A 38.0 kg child swings in a swing supported by two chains, each 3.02 m long. (a) If the tension in each chain at the lowest point is 342 N, find the child's speed at the lowest point. m/s (b) What is the force exerted by the seat on the child at the lowest point? (Neglect the mass of the seat.) N (upward) 2. A typical red blood cell has a mass of 3.0 x10^-16 kg. A blood sample placed in a centrifuge is subjected to a force of 3.2 x 10^-11 N when the centrifuge is operated at 138 rev/s. What is the diameter of the centrifuge? 3. A phonograph record accelerates from rest to 26.0 rpm in 3.63 s. (a) What is its angular acceleration in rad/s^2? Consider the known variables to determine which rotational kinematic equation should be used here. rad/s^2 (b) How many revolutions does it go through in the process? rev

Explanation / Answer

1)a) let the speed be v.so,

balancing the forces,

38*v^2/3.02 + 38*9.81 = 342*2

or v=4.97 m/s

b)force exerted by the seat = 2*342

=683 N

2)mw^2*r=F

or 3*10^-16*(138*2pi)^2*r=3.2*10^-11

or r=0.141 m

so d=2*r=0.282 m

3)w=26*2*pi/60

=2.72 rad/s

angular acceleration = (2.72/3.63)

=0.75 rad/s^2

b) number of revolutions = 0.5*0.75*3.63^2

=4.94 rad

=1.57 revolutions

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