Work Done by a Constant Force Quiz with Answers and Explanations

📚 Quick Study Guide

🔍 Work: Work is done when a force causes a displacement. Mathematically, it's the dot product of force and displacement vectors. 💡 Formula: $W = \vec{F} \cdot \vec{d} = Fd\cos(\theta)$, where $W$ is work, $\vec{F}$ is the force vector, $\vec{d}$ is the displacement vector, $F$ and $d$ are their magnitudes, and $\theta$ is the angle between them. 📝 Units: Work is measured in Joules (J). 1 J = 1 N·m. ➕ Positive Work: Work is positive when the force component is in the same direction as the displacement ($\theta < 90^\circ$). ➖ Negative Work: Work is negative when the force component is opposite to the direction of displacement ($\theta > 90^\circ$). 🚫 Zero Work: Work is zero when the force is perpendicular to the displacement ($\theta = 90^\circ$) or when there is no displacement. 🏋️ Net Work: The net work done on an object is equal to the change in its kinetic energy (Work-Energy Theorem).

🧪 Practice Quiz

1. A box is pulled 5 meters along a horizontal floor with a force of 10 N applied at an angle of 30 degrees above the horizontal. How much work is done on the box?
   1. 50 J
   2. 43.3 J
   3. 25 J
   4. 0 J
2. A 2 kg book is lifted vertically 2 meters. What is the work done by gravity on the book?
   1. 39.2 J
   2. -39.2 J
   3. 0 J
   4. 4 J
3. A car travels 20 meters to the West while being acted upon by a 5 N force directed to the East. How much work is done by the force?
   1. 100 J
   2. -100 J
   3. 0 J
   4. 4 J
4. A force of 20 N is applied to a block, but the block doesn't move. What is the work done?
   1. 20 J
   2. -20 J
   3. 0 J
   4. Insufficient information
5. A person pushes a lawnmower with a force of 80 N at an angle of 60 degrees to the horizontal. If they move the lawnmower 10 meters, how much work do they do?
   1. 800 J
   2. 400 J
   3. 692.8 J
   4. 0 J
6. An object moves at a constant velocity across a frictionless surface. A constant force is applied in the direction of motion. What can be said about the work done?
   1. The work done is positive.
   2. The work done is negative.
   3. The work done is zero.
   4. The work done cannot be determined.
7. A weightlifter lifts a 100 kg barbell a distance of 2 meters straight up. What is the work done by the weightlifter on the barbell?
   1. 1960 J
   2. -1960 J
   3. 0 J
   4. 200 J