Force and Moment of Force Quiz Forces Moments of Force Body Segment Parameters Mass Centre of Mass (or Gravity) Moments of Inertia

1. Which statement best defines the moment of inertia? a) Time immediately before a motion starts. b) Reluctance of a rigid body to linearly accelerate. c) Quantity of angular motion. d) Resistance to change in angular motion.

2. What’s the frictional force on the 20 2. What’s the frictional force on the 20.0 kg box if the coefficient of kinetic friction is 0.700? Assume the applied force causes the object to be moving? a) 196.2 N b) 137.3 N c) 20.0 N d) 14.00 N

a) 15.00 m/s2 b) 9.81 m/s2 c) 8.13 m/s2 d) 162.7 m/s2 3. What’s the acceleration of the 20 kg box if the coefficient of kinetic friction is 0.700 and the applied force is 300 N? Assume the object is moving. a) 15.00 m/s2 b) 9.81 m/s2 c) 8.13 m/s2 d) 162.7 m/s2

a) –16.67 rad/s2 b) –2400 rad/s2 c) –190.0 rad/s2 d) –15.83 rad/s2 4. What is the angular acceleration caused by a frictional force of 200 N on a runner whose centre is 95.0 cm above a level runway if her moment of inertia is 12.00 kg.m2? (Ignore the vertical force.) a) –16.67 rad/s2 b) –2400 rad/s2 c) –190.0 rad/s2 d) –15.83 rad/s2

a) 0.230 kg.m2 b) 1.313 kg.m2 c) 2.63 kg.m2 d) 0.919 kg.m2 5. What is the moment of inertia about its centre of gravity of a 7.5 kg thigh if the thigh’s length is 35 cm and its radius of gyration is 50% of the length? a) 0.230 kg.m2 b) 1.313 kg.m2 c) 2.63 kg.m2 d) 0.919 kg.m2

6. What happens when a resultant force’s line of action passes through the centre of gravity of a body? a) object will continue moving at constant velocity b) object will accelerate in the direction of the force with no change in spin c) object will accelerate linearly and angularly

Correct answers d (resistance to ang. motion) b (=20.0 x 9.81 x 0.70) d (=[200 x 0.95] /12) a (=7.5 x (0.35 x 0.50)2 ) b (linear acceleration only)