(II) A $1.60\text{-m-tall}$ person lifts a $1.65\text{-kg}$ book off the ground so it is $2.20\ \text{m}$ above the ground. What is the potential energy of the book relative to (a) the ground,

(III) The position of a $280\text{-}g$ object is given (in meters) by $x=4.0t^3 - 8.0t^2 - 44t$, where t is in seconds. Determine the net rate of work done on this object (c ) What is the average net power input during the interval from $t=0\ \text{s}$ to $t=2.0\ \text{s}$, and in the interval from $2.0\ \text{s}$ to $4.0\ \text{s}$?

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 the ground.

A 55-kg hiker starts at an elevation of 1600 m and climbs to the top of a 3300-m peak. Can the actual work done be more than this? Explain why.

At room temperature, an oxygen molecule with mass $5.31 \times 10^{-26} \mathrm{~kg}$ has kinetic energy of about $6.25 \times 10^{-21}$ J. Determine the speed of the molecule.

A 55-kg hiker starts at an elevation of 1600 m and climbs to the top of a 3300-m peak. What is the hiker's change in potential energy?

A 55-kg hiker starts at an elevation of 1600 m and climbs to the top of a 3300-m peak. What is the minimum work required of the hiker?

A $1.60-\mathrm{~m}$ tall person lifts a $1.95-\mathrm{kg}$ book off the ground so it is $2.20 \mathrm{~m}$ above the ground. What is the potential energy of the book relative to the top of the person's head?

A $66.5 \mathrm{~kg}$ hiker starts at an elevation of $1270 \mathrm{~m}$ and climbs to the top of a peak $2660 \mathrm{~m}$ high. $(a)$ What is the hiker's change in potential energy? $(b)$ What is the minimum work required of the hiker? $(c)$ Can the actual work done be greater than this? Explain.

(I) How long will it take a $1750\text{-W}$ motor to lift a $335\text{-kg}$ piano to a sizth-story window $18.0\ \text{m}$ above?

A hand exerts a constant horizontal force on a block that is free to slide on a frictionless surface (Fig. 7-36). The block starts from rest at point $\mathrm{A}$, and by the time it has traveled a distance $d$ to point $\mathrm{B}$ it is traveling with speed $v_B$. When the block has traveled another distance $d$ to point $\mathrm{C}$, what will its speed be? Explain your reasoning.

(II) A 1.60-m tall person lifts a 1.95-kg book off the ground so it is 2.20 m above the ground. What is the potential energy of the book relative to How is the work done by the person related to the answers in parts (a) and (b)?

You have two springs that are identical except that spring 1 is stiffer than spring $2\left(k_{1}>k_{2}\right) .$ On which spring is more work done if they are stretched the same distance?

You have two springs that are identical except that spring 1 is stiffer than spring $2\left(k_1>k_2\right)$. On which spring is more work done: (a) if the two springs are compressed using the same force;