A skateboarder of height 1.7 m rides in a straight line for 10 m at nearly constant speed
PHYSICS · Single correct · CBSE · Physics · System of Particles and Rotational Motion · System of Particles and Rotational Motion
Problem
A skateboarder of height 1.7 m rides in a straight line for 10 m at nearly constant speed. The student analyzing the motion decides to treat the skateboarder–skateboard combination as a single point mass located at the system’s center of mass. Which of the following statements most strongly justifies the validity of that choice for determining the skateboarder’s displacement?
(a) Because rotational kinetic energy is negligible whenever motion is along a straight path, the system’s size can be ignored.
(b) The dimensions of the skateboarder–skateboard system are small compared with the 10 m distance traveled, so ignoring size introduces negligible error.
(c) Since the center-of-mass acceleration is essentially zero, every point on the system moves the same distance, making the exact mass distribution unimportant.
(d) The mass of the skateboarder is much larger than that of the skateboard, so treating the whole system as located at the rider’s position yields an accurate displacement.