Question

1. lydia lifts a heavy 3 kg book from the floor to a height of 1.5 m. she then carries the book 8 meters to the stacks and places the book on a lower shelf that is 0.4 meters above the floor. what net work does she to the book?

Explanation:

Step1: Calculate the force due to gravity

The force \(F = mg\), where \(m = 3\space kg\) and \(g= 10\space m/s^{2}\). So \(F=3\times10 = 30\space N\)

Step2: Find the net displacement in the direction of the force

The initial height \(h_1 = 0\space m\) (floor level), the final height \(h_2=0.4\space m\). The net displacement \(d=h_2 - h_1=0.4 - 0=0.4\space m\) (in the direction of the force when lifting or against when lowering, but net displacement is considered).

Step3: Calculate the work done

The work - energy theorem states \(W = F\times d\). Substituting \(F = 30\space N\) and \(d = 0.4\space m\), we get \(W=30\times0.4=12\space J\)

Answer:

\(12\space J\)