Question

A 1.60 m tall person lifts a 2.10-kg book from the ground so it is 2.20 m above the ground. What is the potential energy of the book relative to (a) the ground and (b) the top of the person’s head? How is the work done by the person related to the answers in parts (a) and (b)?

Answer 1

Answer:

Explanation:

Given

mass of book(m)=2.1 kg

height up to which book is lifted is (h)2.2 m

height of person $(h_0)1.6 m$

Potential energy of book relative to ground=mgh

$PE=2.1\times 9.8\times 2.2=45.276 J$

(b)PE w.r.t to person head =mg(h-h0)

$=2.1\times 9.8\times (2.2-1.6)=12.348 J$

work done by person in lifting box 2.2 m w.r.t floor

Word done =Potential Energy of box relative to floor=45.2 J