A child is pulling a wagon down the sidewalk. For 5.0 m the wagon stays on the sidewalk and the child pulls with a horizontal force of 22 N. Then one wheel of the wagon goes off onto the grass so the child has to pull with a horizontal force of 38 N at an angle of 12° to the side for the next 3.0 m. Finally the wagon gets back on the sidewalk so the child makes the rest of the trip, 8.5 m, with a force of 22 N. How much total work did the child do on the wagon?

A 2800-kg space vehicle, initially at rest, falls vertically from a height of 2900 km above the Earth’s surface. Determine how much work is done by the force of gravity in bringing the vehicle to the Earth’s surface.

A package of mass m is placed onto a horizontal conveyor belt moving at speed v (Fig. 7–32). The coefficient of kinetic friction between package and belt is μ_k. How much of this work is done against friction and how much to accelerate the package?

A softball having a mass of 0.25 kg is pitched horizontally at 120 km/h. By the time it reaches the plate, it may have slowed by 10%. Neglecting gravity, estimate the average force of air resistance during a pitch, if the distance between the plate and the pitcher is about 15 m.

A constant force $\vec{F}=(2.0\hat{i}+4.0\hat{j})\text{ N}$ acts on an object as it moves along a straight-line path. If the object’s displacement is $\vec{d}=(1.0\hat{i}+5.0\hat{j})\text{ m}$, calculate the work done by using these alternate ways of writing the dot product:

(a) $W=Fd\cos \theta$; (b) $W=F_x{d}_x+F_y{d}_y$.

An airplane pilot fell 370 m after jumping from an aircraft without his parachute opening. He landed in a snowbank, creating a crater 1.1 m deep, but survived with only minor injuries. Assuming the pilot’s mass was 82 kg and his terminal velocity was 45 m/s, estimate: the work done on him by air resistance as he fell. Model him as a particle.

Consider a force F₁ = $A/\sqrt{x}$ which acts on an object during its journey along the x axis from x = 0.0 to x = 1.0m, where A = 3.0 Nm¹⸍². Show that during this journey, even though F₁ is infinite at x = 0.0, the work W done on the object by this force is finite, and determine W.

A 3.0-m-long steel chain is stretched out along the top level of a horizontal scaffold at a construction site, in such a way that 2.0 m of the chain remains on the top level and 1.0 m hangs vertically, Fig. 7–27. At this point, the force on the hanging segment is sufficient to pull the entire chain over the edge. Once the chain is moving, the kinetic friction is so small that it can be neglected. How much work is performed on the chain by the force of gravity as the chain falls from the point where 2.0 m remains on the scaffold to the point where the entire chain has left the scaffold? (Assume that the chain has a linear weight density of 24 N/m.)

Two forces, ${\vec{F}}_1=(1.50\hat{i}-0.80\hat{j}+0.70\hat{k})\text{ N}$ and ${\vec{F}}_2=(-0.70\hat{i}+1.20\hat{j})\text{ N}$, are applied on a moving object of mass 0.20 kg. The displacement vector of the object while the two forces act is $\overrightarrow{d}=(6.0\hat{i}-8.0\hat{j}+5.0\hat{k})\text{ m}$. What is the work done by the two forces?