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Element of speed time curve
Coasting.
Initial acceleration.
Constant speed.
All of these.
All of these.
A speed-time curve represents the variation of speed of a train with respect to time during a journey. It consists of three primary stages: acceleration, constant speed (or free-running), and retardation (including coasting and braking).
A speed-time curve represents the variation of speed of a train with respect to time during a journey. It consists of three primary stages: acceleration, constant speed (or free-running), and retardation (including coasting and braking).
a=dtdvтАЛ тАФ Rate of change of velocity (Acceleration/Retardation)
v=u+at тАФ Kinematic equation for speed calculation
The speed-time curve reflects the operational phases of electric traction: (1) Acceleration phase where motor torque is high, (2) Constant speed phase where tractive effort balances train resistance, and (3) Coasting phase where the power supply is cut off and the train loses speed due to gravity and friction.
Acceleration phase involves notch-less or notched acceleration for current limiting.
Constant speed phase occurs when tractive effort equals the train resistance.
Coasting is used to save energy by shutting off power and letting the momentum carry the train.
Retardation is the final stage where mechanical/regenerative braking is applied.
Optimizes energy consumption by identifying coasting periods.
Allows calculation of motor rating and power requirements for a specific route.
Calculations are idealized and do not perfectly account for track gradients.
Depends heavily on the mechanical braking characteristics of the rolling stock.
Electric suburban trains
Metro rail systems
Mainline electric locomotives
The shape of the curve changes significantly between urban, suburban, and mainline services.
In urban services, the acceleration and braking periods dominate the curve due to frequent stops.
D is correct тАФ All listed components (coasting, initial acceleration, and constant speed) are fundamental stages of a standard speed-time curve for an electric train.
For competitive exams, remember that urban service curves are characterized by short, frequent acceleration/braking phases with almost no constant speed phase compared to mainline service.