If a body of mass 5 kilograms is dropped freely from a height of 20 meters above the ground, what is its approximate kinetic energy just before striking the surface, assuming negligible air resistance and acceleration due to gravity as 9.8 meters per second squared?

💡 Solution & Explanation

According to the principle of conservation of mechanical energy, the potential energy possessed by the body at the initial height is completely converted into kinetic energy just before it hits the ground. Potential energy is calculated as the product of mass, acceleration due to gravity, and height, which gives 5 multiplied by 9.8 and 20, resulting in 490 joules. Alternative calculations involving incorrect kinematic equations or incorrect mass substitution fail to yield this exact total mechanical energy value. Power is defined as the rate of doing work.