chapter 2 heavy vehicle braking exam questions and answers

heat form of energy in an internal combustion engine motion heat energy produced by engine combustion is converted to in stopping a vehicle, the energy of motion turns the vehicle's wheels, the wheels wont go anywhere unless theres ______ between the tires and the road surface traction what is a car engine heat conversion machine, taking the energy of heat from exploding mixture of fuel and air in the combustion chamber and converting it to motion through the engine crankshaft and drivetrain to the wheels a brake whether it is a brake for a car or commercial vehicle is also a ________but works the opposite to an engine heat conversion machine brakes convert the energy of motion back into the energy of heat through the friction between the brake drums or rotors and the brake lining or pads attached to the wheel is either a drum brake or disc brake that rotates the wheel to stop the vehicle what happens brake linings rub against the brake rotor, creating friction, converting the vehicle's energy of motion into the energy of heat, which stops the vehicle energy going full circle heat energy (from the engine)--> energy of motion (through the drivetrain)--> heat energy (through the brakes) drum brake A brake in which friction is generated by brake shoes being forced against the inside surface of a drum. disc brake A brake in which pressure squeezes the brake pads against a flat metal wheel disc, producing the friction needed to stop the wheel from turning. how much does a typical car weight and have hp 1000 kg and 120 hp heavy trailer tractor combination can weigh up to ______ and have ___ Hp 63,000 kg when loaded and have over 400 hp how to stop the vehicle in less than 7 seconds it required a stopping force of 9 times thet acceleration force -- the equivalent of roughly 4000 hp With a tractor-trailer combination equipped with eight equally loaded axles and 16 brakes, how much does each brake have to provide of the braking force each brake has to provide approximately 1/16 total stopping time drivers perception time, reaction time, brake lag time, braking time see think do see a hazard decide to stop place your foot on the pedal until you stop how long will perception of a problem ahead take 3/4 of a second how long will reaction time of a problem ahead take 3/4 of a second brake lag time air brakes dont stop instantly when you press on the brakes how long is brake lag time with air brakes 4/10s of a second 2 second rule passengers and light truck drivers should watch the vehicles pass some checkpoint on the road drivers of buses, trucks and other large vehicles should never be less than ___ seconds behind the vehicle ahead 5 seconds what do speed and weight affect the stoping power required to stop any vehicle and how far before it stops 2 x vehicle speed requires 4 x stopping power 2 x vehicle weight requires 2x stopping power 2 x vehicle speed and 2 x vehicle weight requires 8 x stopping power how much do brake components heat up to in normal stopping 120 degrees c how much do brake components heat up to in hard braking up to 250 degress c more than 300 degrees c brakes failure what happens as brake drums heat up they expand away from brake linings retarders provide auxiliary slowing effect and assist the main brake system to slow the vehicle 4 main types of retarders engine exhaust hydraulic driveline electric driveline engine retarders engine brakes when is an engine retarder more efficient higher rpm and lower vehicle speed when shoudl you selet your gear shift before going down a hill or you may miss a shift if you wait till you're on the downgrade if you're using retarders on slippery roads be cautious or may cause the wheels to lock up, stalling the engine, and result of a trailer/tractor to jackknife all modern trucks are manufactured to meet safety standard including noise level, so a well maintained engine retarder and properly maintained muffler system shouldn't be noisy tachometer A device used to measure speed of rotation. just before your vehicle comes to a full stop reduce the pressure you're placing on the pedal to prevent the vehicle from jerking back to ensure a smooth controlled stop every time travel at a speed that allows you to see a safe distance ahead, maintain a safe following time or distance, use good braking skills to stop on icy roads use extremely light pressure on the brake to control the vehicles speed, to prevent the wheels from locking up what will a slowly revolving wheel on an icy surface be more effective than a locking wheel skidding on a surface vehicles equipped with an anti lock braking system will require what a different technique for braking on an icy road surface