# Automobile Engineering Questions and Answers – Performance of an Automobile

This set of Automobile Engineering Interview Questions and Answers for freshers focuses on “Performance of an Automobile”.

1. What is the power delivered by the engine to the crankshaft called?
a) Shaft power
b) Horse power
c) Brake power
d) None of the mentioned

Explanation: The total power delivered by the engine to the crankshaft is called Brake power. It can also be defined as the difference between indicated power and friction power.

2. If ‘T’ is torque(in Nm) and ‘N’ is speed(in rpm) then the required expression for Brake power ‘B.P’ in kWs is _________
a) 2πNT/6000
b) 2πNT/60000
c) πNT/6000
d) πNT/60000

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

3. The torque available at the contact between road and driving wheel is called _________
a) Brake power
b) Friction power
c) Tractive effort
d) Engine torque

Explanation: The torque between road and wheel is called tractive effort. Tractive effort is used to describe the pulling capability of an automobile. The tractive force is inversely proportional to the velocity of the vehicle.

4. 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 _______
a) rpm = V/2πR
b) rpm = 2πV/R
c) rpm = πR/V
d) rpm = πV/R

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

5. Which of these is not a power loss which takes place between engine and driving wheel?
a) Power loss due to friction of piston bearings and gears
b) Power loss from clutch to drive wheel due to friction of various parts
c) Transmission line loss
d) None of the mentioned

Explanation: All the above mentioned losses are encountered while transmission of power. About one third of the power of the fuel is wasted due to the friction between different parts of an automobile. This loss can be reduced by using different engine oils.
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6. The force that opposes the motion of a vehicle is _______
a) Rolling resistance
c) Wind or air resistance
d) All of the mentioned

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

7. Rolling resistance doesnot depend on which of the following factors?
c) Wheel inflation pressure

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

8. For an average type of road surface what percentage of vehicle’s weight constitutes rolling resistance?
a) 5 to 10%
b) 1 to 2%
c) 2 to 5%
d) 0 to 3%

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

9. Wind or air resistance depends on which of the following factors?
a) Shape and size of vehicle body
b) Air velocity
c) Speed of vehicle
d) All of the mentioned

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

10. 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 _________
a) A.R = k*A*V^2
b) A.R = k*A*V^3
c) A.R = 2k*A*V
d) A.R = k*A*V

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

11. The value of coefficient of air resistance for average cars is approximately equal to __________
a) 0.32
b) 0.032
c) 0.0032
d) 1.32

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

12. One Horse Power(H.P) is approximately equal to _____ Watts.
a) 810
b) 545
c) 634
d) 746

Explanation: 1 H.P = 746 Watts.

13. Gradient resistance for a vehicle depends on which of the following factors?
a) Weight of the vehicle
b) Size of the vehicle
c) Width of tyres
d) Speed of the vehicle

Explanation: Gradient resistance depends on weight of the vehicle.

14. Power to weight ratio for high performance cars can range up to _______
a) 150
b) 190
c) 230
d) 280

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

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To practice all areas of Automobile Engineering for Interviews, here is complete set of 1000+ Multiple Choice Questions and Answers.

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