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A cricket ball of mass 160 grams was dropped from a height of 50 metres. What would be its kinetic energy just before touching the ground? [use the value of acceleration due to gravity as 10 m/s┬▓ ]
50 joules
80 joules
8 joules
160 joules
80 joules
According to the Law of Conservation of Energy, the potential energy at the top is converted into kinetic energy at the bottom in the absence of air resistance. Therefore, the kinetic energy just before touching the ground is equal to the initial potential energy of the ball.
According to the Law of Conservation of Energy, the potential energy at the top is converted into kinetic energy at the bottom in the absence of air resistance. Therefore, the kinetic energy just before touching the ground is equal to the initial potential energy of the ball.
Think of a swing or a roller coaster: as it descends, it loses height (potential energy) and gains speed (kinetic energy) at the same rate, ensuring the total energy budget remains the same.
PE=mgh тАФ Potential energy formula where m is mass, g is acceleration due to gravity, and h is height
KE=21тАЛmv2 тАФ Kinetic energy formula where m is mass and v is velocity
The principle of conservation of mechanical energy states that the total mechanical energy in an isolated system remains constant. Here, potential energy PE=mgh at the height h is converted entirely into kinetic energy KE=21тАЛmv2 at the point of impact.
Mass must be converted to SI units: 160┬аg=0.16┬аkg.
Energy is measured in Joules (J).
Conservation of energy assumes negligible air resistance.
Projectile motion calculations
Design of power generation dams (water head to kinetic energy)
Calculation: PE=0.16┬аkg├Ч10┬аm/s2├Ч50┬аm=80┬аJ.
Option A, C, and D are incorrect as they result from calculation errors or improper unit conversion.
B is correct тАФ The kinetic energy at the ground is equal to the initial potential energy, which is 0.16├Ч10├Ч50=80┬аJ.
Always ensure mass is in kilograms (kg) and distance in meters (m) before calculating energy in Joules (J) to avoid unit conversion errors.
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