Q: Explain advantages and disadvantages of friction. (8 marks)
A: Safe walking on the floor, motion of vehicles are possible due to friction.
Nails, Screws are driven into walls due to friction. Mechanical Power
transmission of belt drive is possible due to friction.
Disadvantages:
Due to friction wear and tear of mechanics increases.
Heat generated due to friction, decreases the efficiency of engine.
Friction results in the large amount of power loss in engines.
Q: Mention the methods used to decrease friction.
A: Polishing: By polishing the surfaces of contact, friction can be reduced.
Bearings: The hard steel balls called bearings placed between the
moving parts converts sliding friction into rolling friction hence
friction is reduced.
Lubricants: Lubricants like oil or grease which spreads over the
surface and fills the irregularities of the surface, there by friction
is reduced.
Streamlining: Automobiles and aeroplanes are streamlined to reduce the
friction due to air.
2 Marks Questions:
Q: What is inertia? What gives the measure of inertia?
A: The inability of a body to change its state of rest or state of
motion by itself is known as inertia. Mass is measure of inertia.
Q: If a bomb at rest explodes into two pieces, the pieces must travel
in opposite directions. Explain.
A: According to Law of Conservation of linear momentum MU = m1v1 +
m2v2 Initially bomb is at rest U = 0
∴ m1v1 = − m2v2
−ve sign indicates that pieces must travel in opposite direction.
Q: Can the coefficient of friction be greater than one?
A: Yes, when the contact surfaces are heavily polished, then the
adhesive forces between molecules increases and coefficient of
friction will be greater than one.
Q: Why does the car with a flattened tyres stop sooner than the one
with inflattened tyres?
A: Flattened tyre deforms more than inflattened tyre. Due to greater
deformation of tyre rolling friction is large, hence it stops sooner.
PGRRCDE Osmania University Admissions 2015-16
Prof G Ram Reddy Center for Distance Education (PGRRCDE), Osmania University Campus, Hyderabad has issued notification for admission into BA, B.Com, BBA, MA, M.Sc, M.Com, MBA and MCA for the academic session 2015-16.
PG Diploma courses: Maths, English, Business Management, Computer Applications, Bioinformatics, Town and Country Planning.
Candidates can obtain application forms in person or by post from Director, PGRRCDE, OU. Forms can also be downloaded from the website www.osmania.ac.in .
Last date for the submission of filled in applications is 7th October 2015. Website for downloading applications and other information is oucde.ac.in OR www.oucde.net .
PG Diploma courses: Maths, English, Business Management, Computer Applications, Bioinformatics, Town and Country Planning.
Candidates can obtain application forms in person or by post from Director, PGRRCDE, OU. Forms can also be downloaded from the website www.osmania.ac.in .
Last date for the submission of filled in applications is 7th October 2015. Website for downloading applications and other information is oucde.ac.in OR www.oucde.net .
NTR Health University Ph.D Admissions 2015-16
Dr NTR University of Health Sciences (NTRUHS), Vijayawada, Andhra Pradesh has announced notification for admission into Ph.D course for the academic year 2015-16. The course is offered in medical sciences or allied subjects.
Filled in applications have to reach the NTR University on or before 20th October 2015. The details of eligibility, selection and application procedure are available on the website ntruhs.ap.nic.in .
The course is offered in full time and part time modes. Candidates should have Masters Degree (MD / MS / DNB / MDS / MD Ayurveda / M.Sc (N) / MPT / M.Sc Medical in any any subject allied to medical sciences of NTRUHS / M.Phil etc.
Application forms can be downloaded from the NTRUHS website from 26th September 2015. Last date is 5th October 2015. List of eligible candidates will be displayed on the website on 11 November 2015.
Filled in applications have to reach the NTR University on or before 20th October 2015. The details of eligibility, selection and application procedure are available on the website ntruhs.ap.nic.in .
The course is offered in full time and part time modes. Candidates should have Masters Degree (MD / MS / DNB / MDS / MD Ayurveda / M.Sc (N) / MPT / M.Sc Medical in any any subject allied to medical sciences of NTRUHS / M.Phil etc.
Application forms can be downloaded from the NTRUHS website from 26th September 2015. Last date is 5th October 2015. List of eligible candidates will be displayed on the website on 11 November 2015.
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