Suppose that you can lift no more than 650 N (around 150 lb) unaided.
(a) How much can you lift using a 1.4-m-long wheelbarrow that weighs 80.0 N and whose center of gravity is 0.50 m from the center of the wheel (Fig. E11.16)? The cen-ter of gravity of the load car-ried in the wheelbarrow is also 0.50 m from the center of the wheel. (b) Where does the force come from to enable you to lift more than 650 N using the wheelbarrow?

Verified step by step guidance

1. Step 1: Identify the forces acting on the wheelbarrow. These include the weight of the wheelbarrow (80.0 N) and the weight of the load (which we need to find).
2. Step 2: Determine the distances from the pivot point (the wheel) to the center of gravity of the wheelbarrow and the load. Both are given as 0.50 m.
3. Step 3: Use the principle of moments (torque) to set up the equation. The sum of the moments about the pivot point must be zero for the system to be in equilibrium. The moment due to the weight of the wheelbarrow and the load must be balanced by the moment due to the lifting force.
4. Step 4: Set up the equation: (Weight of wheelbarrow * distance from pivot) + (Weight of load * distance from pivot) = (Lifting force * distance from pivot). Substitute the known values: (80.0 N * 0.50 m) + (Weight of load * 0.50 m) = (650 N * 1.4 m).
5. Step 5: Solve for the weight of the load. Rearrange the equation to isolate the weight of the load and solve.

Key Concepts

Torque

Torque is a measure of the rotational force applied to an object, calculated as the product of the force and the distance from the pivot point (lever arm). In the context of the wheelbarrow, the torque generated by the load and the wheelbarrow's weight must be balanced by the torque exerted by the person lifting it. Understanding torque is essential for analyzing how much weight can be lifted using the wheelbarrow.

Equilibrium

Equilibrium occurs when all forces and torques acting on an object are balanced, resulting in no net force or rotation. In the case of the wheelbarrow, the system is in equilibrium when the upward force exerted by the person equals the downward forces from the load and the wheelbarrow's weight. This concept is crucial for determining how much weight can be lifted without tipping the wheelbarrow.

Mechanical Advantage

Mechanical advantage is the factor by which a machine multiplies the force applied to it, allowing a user to lift heavier loads with less effort. The wheelbarrow provides mechanical advantage by allowing the user to apply force at a distance from the pivot point (wheel), effectively lifting more weight than they could unaided. This principle explains how the user can lift more than their unaided limit of 650 N.