Questions set 78

Braking System

1.      In a disc brake, which component provides the pad-to-disc adjustment?
a) Bleed screw
b) Piston
c) Caliper
d) Piston seal
Answer: d
Explanation: Piston seal provides the pad-to-disc adjustment in a disc brake. When the brake is applied, the piston seal deforms.

2.      What is the braking torque at leading shoe if resultant frictional force acts at a distance of 250 mm from the brake drum center, coefficient of friction between the shoe and the drum as 0.5, the free ends of the two shoes are pushed apart with a force of 300 N which is acting at a distance of 320 mm from anchor, and two shoes are anchored together 170 mm away from the brake drum center?
a) 276.6 Nm
b) 256.6 Nm
c) 266.6 Nm
d) 246.6 Nm
Answer: c
Explanation: T_L =W∗L∗μ∗RM−(μ∗R)=320∗300∗0.5∗250170−(0.5∗250) = 266666.66 Nmm = 266.6 Nm where L is the distance at which the force acts from the anchor, W is the force from the anchor, μ is the coefficient of friction, R is the distance of resulting friction force from brake drum center, M is the distance between the two anchors.

3.      On what principle does the braking system in the car work?
a) Frictional force
b) Gravitational force
c) Magnetic force
d) Electric force
Answer: a
Explanation: Frictional force is the main force which acts and plays an important role in the braking system. The disc pads get to rub against the drum and which creates the friction and opposes the motion of the rotational motion of the drum.

4.      Generally which brakes are on the front wheels?
a) Drum brake
b) Disk brake
c) Shoe brake
d) Double shoe brake
Answer: b
Explanation: Disk brakes are used usually on the front wheels. When the brakes are applied the 70% of the weight is transferred to the front wheels. Because of which the brakes on the front wear out faster.

5.      If the car is moving on the level road at a speed of 50 km/h has a wheelbase 3 m, a distance of C.G. from ground 700 mm and distance from rear wheels is 1.1 m. Coefficient of friction is 0.7. What is the retardation if the brakes are applied to the rear wheels?
a) 3.7 m/s²
b) 2.7 m/s²
c) 1.7 m/s²
d) 4.7 m/s²
Answer: a
Explanation: When the brakes are applied on the rear wheels and the vehicle is moving on the level road, a = μ∗g∗(L−x)L+μ∗h where ‘μ’ is the coefficient of friction, ‘L’ is wheelbase, ‘x’ is a distance of C.G. from rear wheels, and ‘h’ is the distance of the C.G. from the surface of the road. Therefore a = 0.7∗9.81∗(3−1.1)3+(0.7∗0.7) = 3.7 m/s².

6.      If the car is moving on the level road at a speed of 50 km/h has a wheelbase 4 m, a distance of C.G. from ground 800 mm and distance from rear wheels is 1.2 m. Coefficient of friction is 0.8. What is the retardation if the brakes are applied to the front wheels?
a) 3.4 m/s²
b) 2.4 m/s²
c) 1.4 m/s²
d) 4.4 m/s²
Answer: b
Explanation: When the brakes are applied on the front wheels and the vehicle is moving on the level road, a = μ∗g∗xL−μ∗h where ‘μ’ is the coefficient of friction, ‘L’ is wheelbase, ‘x’ is a distance of C.G. from rear wheels, and ‘h’ is the distance of the C.G. from the surface of the road. Therefore a = 0.7∗9.81∗1.24−(0.8∗0.8) = 2.4 m/s².

7.      If the car is moving on the level road at a speed of 50 km/h has a wheelbase 4 m, a distance of C.G. from ground 800 mm and distance from rear wheels is 1.2 m. Coefficient of friction is 0.8. What is the retardation if the brakes are applied to all wheels?
a) 7.8 m/s²
b) 6.8 m/s²
c) 5.8 m/s²
d) 4.8 m/s²
Answer: a
Explanation: When the brakes are applied on all wheels and the vehicle is moving on the level road, a = μ*g where ‘μ’ is the coefficient of friction, ‘L’ is wheelbase, ‘x’ is a distance of C.G. from rear wheels, and ‘h’ is the distance of the C.G. from the surface of the road. Therefore a = 0.8 * 9.81 = 7.8 m/s².

8.      The car is moving up on the 12o inclined road with horizontal at 36 km/h which is having wheelbase 1.4 m. The C.G. of the car is 0.9 m above the road. The coefficient of friction is 0.7. What is the retardation of the car if the brakes are applied to all the four wheels?
a) 8.75 m/s²
b) 8.81 m/s²
c) 7.71 m/s²
d) 6.81 m/s²
Answer: a
Explanation: α is the inclination angle in degree = 12°, μ is the coefficient of friction = 0.7. When the vehicle is moving up on the inclined road and brakes are applied to all four wheels than the retardation a = g*(μ*cosα + sinα) = 9.81*(0.7*cos12° + sin12°) = 8.75 m/s².

9.      The car is moving down on the 14° inclined road with horizontal at 36 km/h which is having wheelbase 1.4 m. The C.G. of the car is 0.9 m above the road. The coefficient of friction is 0.75. What is the retardation of the car if the brakes are applied to all the four wheels?
a) 4.76 m/s²
b) 5.76 m/s²
c) 6.76 m/s²
d) 7.76 m/s²
Answer: a
Explanation: α is the inclination angle in degree = 14° μ is the coefficient of friction = 0.75. When the vehicle is moving down on the inclined road and brakes are applied to all four wheels than the retardation a = g*(μ*cosα – sinα) = 9.81*(0.75*cos14° – sin14°) = 4.76 m/s².

10.  The metering valve is used to proportion the braking effect between the front and the rear axle.
a) True
b) False
Answer: b
Explanation: The proportioning valve is used to proportion the braking effect between the front and the rear axle.