1. **Describe the car's motion.** The car experiences forces: Left is 6000 N, Right is 8000 N, Up is 2000 N, Down is 2000 N. Net force horizontally: $8000 - 6000 = 2000\ \text{N to the right}$. Vertically, forces cancel: $2000 - 2000 = 0$. Since net force right is positive, the car is speeding up forward. 2. **Find net force on each box.** Box A: Left 60 N, Right 20 N. Net force: $20 - 60 = -40 \text{N}$ (left). Box B: Up 50 N, Down 25 N. Net force: $50 - 25 = 25 \text{N}$ (up). 3. **Find the fourth scale reading.** Total weight = 1500 N. Three scales sum: $400 + 300 + 250 = 950 \text{N}$. Fourth scale reading = $1500 - 950 = 550 \text{N}$. 4. **Compare inertia of bowling ball to tennis ball.** Inertia proportional to mass. Mass bowling ball = 6 kg, tennis ball = 0.06 kg. Ratio = $\frac{6}{0.06} = 100$. Bowling ball has 100 times more inertia. 5. **Draw free-body diagrams.** a. Net force 100 N right means push force right minus friction left = 100 N. b. Refrigerator in equilibrium means push force = friction force. Net force = 0 N. 6. **Find acceleration of 100 kg bag of sand.** Weight $W = mg = 100 \text{N}$, so $m=100/9.8 \approx 10.2 \ \text{kg}$. In free fall, acceleration $a = g = 9.8 \ \frac{m}{s^2}$. Final Answers: 1. Speeding up forward. 2. Box A: 40 N left; Box B: 25 N up. 3. Fourth scale: 550 N. 4. Bowling ball has 100 times inertia. 5a. Net force 100 N right; 5b. Net force 0 N. 6. Acceleration $9.8 \ \frac{m}{s^2}$.