The velocity 'V' reached by a car of mass 'm' at certain distance from the starting point driven with constant power 'P' is such that
Correct answer: C. V^3α 3P/m
- A. Vα 3P/m
- B. V^2 α 3P/m
- C. V^3α 3P/m
- D. Vα (3P/m)^2
Explanation
Here's how we can find the relationship between the velocity (V), mass (m), power (P), and distance (x):1. Work-Energy Principle:We know that the work done (W) by the engine is equal to the change in kinetic energy (ΔKE) of the car:W = ΔKE2. Work Done by the Engine:The work done by the engine (W) can be calculated using the following equation:W = P * twhere:P is the constant powert is the time taken to travel the distance3. Change in Kinetic Energy:The change in kinetic energy (ΔKE) can be calculated using the following equation:ΔKE = 1/2 * m * V^2where:m is the mass of the carV is the final velocity of the car4. Relating Distance and Time:Since the power is constant, we can relate the distance (x) traveled by the car to the time (t) using the following equation:P = F * Vwhere:F is the force acting on the carV is the instantaneous velocity of the carAs the car accelerates, the velocity (V) increases. However, for a small distance increment (dx), we can assume the velocity to be constant. Therefore, we can write:dx = V * dtIntegrating both sides over the entire distance (x):x = ∫ V * dt = ∫ (P / F) * dtSince power (P) and mass (m) are constant, we can take them outside the integral:x = (P / m) * ∫ 1/V * dt5. Combining Equations:Substituting the expressions for work (W) and change in kinetic energy (ΔKE) from equations 2 and 3 into the work-energy principle (equation 1):P * t = 1/2 * m * V^2Substituting the expression for time (t) from equation 4:P * ((x * m) / (P)) = 1/2 * m * V^2Simplifying:2x = V^26. Solving for Velocity:Taking the square root of both sides:V = √(2x)Cubing both sides:V^3 = 2^3 * x = 8xNow, substituting the expression for x from equation 4:V^3 = 8 * (P / m)Multiplying both sides by the constant α (which represents a proportionality constant):V^3 * α = 8α * (P / m)Therefore, the correct relationship between the velocity (V), mass (m), power (P), and distance (x) is V^3 * α * 3P / m, which corresponds to option (c).
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Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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