needs help inthis question.I think the answer is (a)?
2. You are standing in a moving bus, facing forward, and you suddenly fall forward.
What force caused you to fall forward?
A) gravity
B) normal force due to your contact with the floor of the bus
C) force due to friction between you and the floor of the bus
D) There is not a force leading to your fall.
i think it wud b none of these…it wud be somthing called inertia of motion!
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The Importance of Using Regulation Compliant Brakes
The following headlines are extracted from articles and news sites, and serve as a couple of examples where brake failure has been identified as the major cause of accidents and potential deaths on South African roads. Taxis and buses are however not the only culprits. Every vehicle owner that service their own vehicle, using counterfeit brake pads in order to save a couple of Rand, risk not only their own lives but also those of their families and other drivers on the road.
“January 2004 Bad brakes make trucks death traps”
Seventy percent of trucks inspected by road traffic police during a blitz operation on KwaZulu-Natal roads last week were found to have defective brakes….
“November 2004 – ‘Death-trap taxis have no place on our roads’ (2004)”
The traffic officers thought it was a can of cooldrink on the minibus taxi’s dashboard – but they were about to be stunned. They found there was a pipe attached to the can that led to the brake fluid reservoir in the engine compartment. The driver was continuously pouring brake fluid into the can while driving. This was just one of the horrifying defects found by Johannesburg Metro Police Department (JMPD) officers conducting raids on taxis as part of their 500-day Operation Token Days, which includes the blitzing of taxis at ranks… (Ref. IOL.co.za, 5 November 2004)
Radebe blames brake failure in bus accidents (2006)
Brake failure was a major factor in a recent spate of bus accidents, Transport Minister Jeff Radebe said on Thursday. “Buses involved in these accidents are clearly old and not roadworthy,” he told a SA Bus Operators Association (Saboa) conference in Pretoria. In some instances, buses were fitted with new parts to pass roadworthy tests, after which they were removed. Operators whose buses crashed because of negligence, recklessness and unroadworthiness would be held responsible, he warned. Radebe said all bus operators receiving state subsidies will have to renew their fleets and undergo regular testing at authorised facilities…
When should I replace my brakes?
Symptoms of brake failure:
1.Noises
Your brake system may be crying for help if you’re hearing strange noises when you depress the brake. Two of the most common are squeaks and grinding.
2.Squeaks
Friction from the brake lining causes heat. Under extreme conditions this can damage the pads and/or lining, brake drums and rotors.
3.Grinding
Metallic grinding sounds indicate your brake pads are worn through. Metal-to-metal contact will damage drums or rotors.
4.Low or Fading Brake Pedal
Do your brakes require pumping to stop the car? Does the pedal sink to the floorboard when you’re stopped at a light? There may be a leak in the brake system, air in the brake lines, or the need for a brake adjustment.
5.Pulling to one side or brake drag
Worn or uneven brake linings or a damaged brake line can cause your vehicle to pull to one side. Brakes that are out of adjustment or have contaminated fluid can cause brakes to drag.
Brake testing and the importance of brake pad certification ECE R 90 and VC8053
ECE R90 is a European standard for brake components that requires brake manufacturers to conform and guarantee to the original equipment standards as far as performance and quality is concerned. Products complying to these standard carry an “E” mark on products and packaging. In Europe brake pads cannot be used or sold unless they carry this mark proving that they performance and quality standards compliant.
Most countries around the world are following suit by setting standards to which brake pads have to comply.
Regulation VC8053 is minimum specification published in the Government gazette No. 22014 of 2 February 2001, to which brake lining assemblies in South Africa has to comply and this specification is regulated by the SABS.
The tests for both these regulations consist of laboratory and road tests we will not go into detail about it but rather summarize the requirements:
Brake pad road tests:
1.A series of 0-type standardisation tests braking suddenly under different conditions of vehicle speed and load with the aim to test the correct response in emergencies, parking and different braking situations.
2.Loss of efficiency when warmed up In the first test the brake is used 15 times in succession to test its performance under different conditions. In the process, the brake warms up. In the last instance its performance is measured and checked for correct operation after which the results are compared to brake performance when the brakes are cold.
3.Speed-sensitivity test The pressure is identified in the previous test to obtain a deceleration of 5m/s2. The same kind of test is repeated at 65 km/h, 90km/h and 135km/h in order to check that the brake’s deceleration is maintained irrespective of the speed at which the vehicle is traveling.
Brake pad laboratory tests:
Once the road tests are completed, mechanical laboratory tests are done:
1.Compressibility test the compressibility of the brake pad should not exceed 5% of its thickness at 400 deg. C.
2.Resistance to brake seizure this test simply determines the adherence of the friction material to the metal support.
Once the tests are completed an approval number is issued and it is compulsory that the brake pads and packaging contain the specific number example: E1 XXXXX. Packaging should be tamper proof and contain instructions in the local language where the product will be sold.
Standards compliant brake pads will not only ensure roadworthy vehicles but also ensure safety for both the driver and their passengers when it is needed most. So all vehicle owners are urged to ensure that the replacement brake pads they purchase complies to industry requirements and standards.
About the Author
About ECE90:
ECE90 Brake testing (Pty) Ltd certification service for replacement brake lining assemblies laboratory is based in South Africa and provides local and International brake testing facilities. =>Add your comments at: ECE 90 brake testing
