PHYSICS
WORKSHEET
ROTATIONAL MOTION A
NAME: _______________________________
1. A beetle standing on the edge of 12- inch 2 kg disk is whirling around at 33 1/3 rotations per minute.
A. Compute the magnitude of the creature’s angular velocity. (there are 2.54 cm in an inch)
ϴ=33.33
ω=?
t = 60 s
ϴ=33.33 x 2πrad = 209.31 rads
3.48 rad/s
ω = ϴ/t
ω = 209.31/60 =
B. Compute the magnitude of the creature’s centripetal acceleration.
d=12 in
r = 6 in
1.85 m/s2
ac = r ω
2
r = 2.54 cm/in (6 in) = 15.2 cm =0 .152 m
ac = (0.152 m) (3.48 rad/s)2 = 1.85
C. Neglecting the mass of the beetle, what is the rotational inertia of the disk?
m = 2 kg
I = mr2
I = 2 kg x (0.152 m)2 = 0.046 kgm2
D What is the angular momentum of the disk?
L = Iω
2.
L = (0.046 kgm2)( 3.48 rad/s) = 0.160 kg∙m2/s
If a torque of 55.0 N∙m is required and the largest force that can be exerted by you is 135 N, what is the length of
the lever arm that must be used?
0.407 m
T =55 N∙m
F = 135 N
r=?
T/F =r
55/135 =
PHYSICS
WORKSHEET
ROTATIONAL MOTION B
NAME: _______________________________
1.
What is the angular momentum of a 6 kg mass traveling with a speed of 6 m/s in a circle of radius of 12 m?
432 kg·m2/s
2.
If the torque required to loosen a nut on a wheel has a magnitude of 40.0 N·m and the force exerted by a mechanic
is 133 N, how far from the nut must the mechanic apply the force?
0.3 m
3.
A bowling ball has a mass of 7.0 kg, a moment of inertia of 2.8 ´ 10–2 kg·m2, and a radius of 0.10 m. If it rolls
down the lane without slipping at an angular speed of 4.0 ´ 101 rad/s, what is its angular momentum?
1.1 kgm2/s
4.
A figure skater with arms drawn in spins on the ice at a rate of 5.0 rad/s and has an angular momentum of 9.4
kg·m2/s. What is the skater’s rotational inertia .
1.875 kg•m2
Extra Credit
Gerry, whose mass is 43 kg, sits 1.8 m from the center of a seesaw. Steve, whose mass is 52 kg wants to balance Gerry.
How far from the center of the seesaw should Steve sit?
1.5 m