Question

1. which statement explains how it is possible to carry books to school without changing the kinetic or potential energy of the books or doing any work?

a. by moving the book without acceleration and keeping the height of the book constant
b. by moving the book with acceleration and keeping the height of the book constant
c. by moving the book without acceleration and changing the height of the book
d. by moving the book with acceleration and changing the height of the book

Explanation:

To solve this, we analyze each option:

• Kinetic energy ($KE = \frac{1}{2}mv^2$) depends on velocity. No acceleration means constant velocity (so $KE$ constant). Potential energy ($PE = mgh$) depends on height ($h$); keeping $h$ constant keeps $PE$ constant. Work done against gravity is $W = mgh$ (if $h$ changes) or work due to force and displacement. If moving without acceleration (net force = 0, so applied force balances other forces) and $h$ constant, then:
• Option a: Moving without acceleration (constant velocity, so $KE$ same) and constant height (so $PE$ same). Also, work done on the book (in terms of changing its energy) would be zero since $KE$ and $PE$ don't change.
• Option b: Acceleration means velocity changes, so $KE$ changes (invalid).
• Option c: Changing height changes $PE$ (invalid).
• Option d: Acceleration changes $KE$, changing height changes $PE$ (invalid).

Answer:

a. By moving the book without acceleration and keeping the height of the book constant