Performance of an Automobile

·         What is actual power delivered by the engine known as?

Answer: The power delivered by the engine is called brake power.

·         If ‘T’ is torque(in Nm) and ‘N’ is speed(in rpm) then the required expression for Brake power ‘B.P’ in kWs is

Answer: The required expression is B.P = 2πNT/60000.

·         The torque available at the contact between road and driving wheel is called

Answer: The torque between road and wheel is called tractive effort.

·         If ‘V’ is vehicle speed(in metres/min) and ‘R’ is radius of driving wheel(in metres) then the rpm of the driving wheel is given by

Answer: The rpm of the driving wheel can be expressed as rpm = V/2πR.

·         Which of these is not a power loss which takes place between engine and driving wheel

Answer: All the above mentioned losses are encountered while transmission of power.

·         The force that opposes the motion of a vehicle is

Answer: Rolling resistance, gradient resistance and air resistance all oppose the motion of a vehicle.

·         Rolling resistance does not depend on which of the following factors

Answer: Rolling resistance does not depend on radius of driving wheel.

·         For an average type of road surface what percentage of vehicle’s weight constitutes rolling resistance

Answer: On an average road surface rolling resistance is 1 to 2% of vehicle’s weight.

·         Wind or air resistance depends on which of the following factors

Answer: Air resistance on a vehicle depends on all the above mentioned factors.

·         If ‘k’ is coefficient of air resistance, ‘A’ is frontal area projected by the vehicle in square metres and ‘V’ is vehicle speed(in km/h) then the expession for air resistance ‘A.R’ on the vehicle is

Answer: The correct expression for air resistance is A.R = k*A*V².

·         The value of coefficient of air resistance for average cars is approximately equal to

Answer: For average cars, value of coefficient of air resistance is approx 0.0032.

·         One Horse Power(H.P) is approximately equal to _____ Watts.

Answer: 1 H.P = 746 Watts.

·         Gradient resistance for a vehicle depends on which of the following factors

Answer: Gradient resistance depends on weight of the vehicle.

·         Power to weight ratio for high performance cars can range upto

Answer: The ratio of power to weight of high performance cars can range as high as 230.