Rotational Motion
Answers
Unit 6: Uniform Circular Motion & Orbital Motion
Q6.1) a) 12.6 N
b) 10 m/s
Q6.2) 13.8 revolutions
Q6.3) a) 21 690 N [up]
b) 15 810 N [down]
Q6.4) 28 984 m/s
Q6.5) a) 3.88x10⁻⁷ m/s² [left]
b) 0
c) 6.13x10⁻⁷ m/s²
Q6.6) 5066 seconds or 84.4 minutes
Q6.7) 3.59x10⁷ m
Q6.8) 4.05 degrees
Q6.9) a) 7.5 m
b) 29.6 m
Q6.10) 0.0249 Hz or 1.49 rpm
Unit 7: Rotational Kinematics
Q7.1) a) 4320°
b) 24𝜋 rads or 75.4 rads
c) 188.5 m
d) 0.838 rads/s
Q7.2 a) -0.393 rads/s²
b) Friction between the top’s tip and the surface on which it spins, and friction between the top’s sides and the air through which it spins.
Q7.3) 3 m
Q7.4) 9.3 s
Q7.5) 7.11 s
Q7.6) a) 131.8 rads/s
b) 52.7 m/s
c) 517.3 m
Unit 8: Moment of Inertia
Q8.1) A
Q8.2) It decreases
Q8.3) It would increase
Q8.4) It would increase
Q8.5) a) 2 kg m²
b) 2 kg m²
c) 4 kg m²
Q8.6) a) 3.11 kg m²
b) 1.11 kg m²
c) 0 kg m²
Q8.7) 31 756 amu pm²
Unit 9: Torque & Rotational Mechanics
Q9.1) a) 20 Nm
b) 17.3 Nm
c) 0 Nm
d) -10 Nm
Q9.2) 8820 N
Q9.3) 0.62 m
Q9.4) 1000 m
Q9.5) 230 kg
Q9.6) 16.7 cm
Q9.7) The top hinge exerts a force of 168 N leftward on the door. The bottom hinge has an x-component of 168 N rightward and a y-component of 588 N upward, which combine to give a 612 N force that points 74 degrees above the horizontal.
Unit 10: Energy of Rotating Bodies
Q10.1) a) 1.98 J
b) 1.98 J
c) 3.96 J
Q10.2) 11.4 m/s
Q10.3) 5.16 m
Q10.4) 88.5 rads/s
Unit 11: Conservation of Angular Momentum
Q11.1) 0.314 kg m² /s
Q11.2) 1.98 rads/s
Q11.3) a) Increases by 43%
b) Increases by 43%