I am a full time tutor specialising in JC H2 Physics and H1 maths, O level Physics, Elementary Maths, Additional Maths, Chemistry , Lower Secondary Maths and Science .
I have more than 5 years of teaching experience for secondary to Jc levels and have helped students improved grades from F9 to A2 for O level and ungraded to B for A level.
Sample of my physics notes is given below :
Work and Energy
1. Object thrown upward vertically :
Work is done against gravity = mgh where m is the mass of object , g = gravitational field strength and h is height reached . This is the amount of KE converted to PE at maximum height.
Work is also done against air resistance = Integration of f over dx where f= frictional force (which may not be constant ) and x is the vertical distance travelled . This is the amount of KE converted to heat. If f is constant then this work = fh for height reached =h
So KE lost = mgh + fh = PE gained + heat generated
KE lost is also = work done against gravity (=mgh) and work done against air resistance (=fh).
In short work done results in the conversion of one form of energy into another and the amount of work done = amount of energy converted .
2. Object of mass m released from rest from height h , when it hits the ground :
PE lost = mgh
KE gained = 1/2 mv^2
Heat generated = fh (assuming constant frictional force f)
So PE lost = mgh = KE gained + heat generated = 1/2mv^2 + fh
Work done = PE lost = KE gained and heat generated
3. Object moving horizontally a distance d with initially velocity v , when it stops :
KE lost = 1/2mv^2 = heat generated = fd where f is the average frictional force .
In this case PE change = 0.
4. Moon or satellite going round earth
In the case of an object moving with constant velocity and without change in PE, work done = 0. For example the moon or satellite going round earth at constant velocity and fixed orbit is not doing any work .
Tangential to its orbit there is no force though there is tangential displacement hence work done tangentially is 0.
Radially , there is centripetal force due the gravity but radial displacement is 0 hence work done = 0
Hence both the PE and KE of the moon or satellite remain constant
5. A plane cruising at height h with constant velocity v
Work done = fd where f is average air resistance .
PE change = 0 as h is constant , KE change = 0 as v is constant .
This is how even if the plane engine fails it can glide over some distance till the drag slows it down so much that the velocity drops to a level that generates insufficient lift to balance its weight then it will crash down .
I hope to provide an effective tuition service .
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