A Vehicle Saves Energy

📌 CONCEPT: The work done against gravity is the energy expended to overcome the gravitational potential energy difference between the initial and final positions of the vehicle.

📐 RULE / FORMULA: Work done (W) against gravity can be calculated using the formula W = mgh, where m is the mass of the vehicle, g is the acceleration due to gravity, and h is the height through which the vehicle moves.

💡 WORKED EXAMPLE: If a car weighs 1500 kg and climbs a 10 m high slope, calculate the work done against gravity. Given g = 9.8 m/s^2, W = 1500 * 9.8 * 10 = 147000 J. Now, if the car's engine speed drops to 800 rpm, the work done remains the same as the mass and height remain unchanged.

⚠️ COMMON MISTAKE: Students often forget to consider the change in potential energy when the car's engine speed changes, leading to incorrect work done calculations.