Questions set 53

Performance of an Automobile

1.      What is actual power delivered by the engine known as?
a) Shaft power
b) Horse power
c) Brake power
d) None of the mentioned
Answer: c
Explanation: The power delivered by the engine is called brake 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
Answer: b
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
Answer: c
Explanation: 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
a) rpm = V/2πR
b) rpm = 2πV/R
c) rpm = πR/V
d) rpm = πV/R
Answer: a
Explanation: The rpm of the driving wheel can be expressed as rpm = V/2πR.

4.      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
Answer: d
Explanation: All the above mentioned losses are encountered while transmission of power.

5.      The force that opposes the motion of a vehicle is
a) Rolling resistance
b) Gradient resistance
c) Wind or air resistance
d) All of the mentioned
Answer: d
Explanation: Rolling resistance, gradient resistance and air resistance all oppose the motion of a vehicle.

6.      Rolling resistance doesnot depend on which of the following factors
a) Load on each road wheel
b) Radius of driving wheel
c) Wheel inflation pressure
d) Nature of road surface
Answer: b
Explanation: Rolling resistance does not depend on radius of driving wheel.

7.      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%
Answer: b
Explanation: On an average road surface rolling resistance is 1 to 2% of vehicle’s weight.

8.      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
Answer: d
Explanation: Air resistance on a vehicle depends on all the above mentioned factors.

9.      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

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

10.  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
Answer: c
Explanation: For average cars, value of coefficient of air resistance is approx 0.0032.

11.  One Horse Power(H.P) is approximately equal to _____ Watts.
a) 810
b) 545
c) 634
d) 746
Answer: d
Explanation: 1 H.P = 746 Watts.

12.  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
Answer: a
Explanation: Gradient resistance depends on weight of the vehicle.

13.  Power to weight ratio for high performance cars can range upto
a) 150
b) 190
c) 230
d) 280
Answer: c
Explanation: The ratio of power to weight of high performance cars can range as high as 230.