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PHYSICS > WORK, POWER, ENERGY > Flashcards

WORK, POWER, ENERGY Flashcards

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1
Q

define work

A

when a force is applied on a body and it covers some displacement in the direction of force.

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2
Q

at which angle, work done is zero

A

at 90°

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3
Q

at which angle is work done maximum and positive

A

0°

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4
Q

at which angle is work done half of the maximum value

A

60°

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5
Q

at which angle is work done maximum and negative

A

180°

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6
Q

what are the SI units of work

A

joule

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7
Q

base units of work

A

Nm or kgm^2/s^2

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8
Q

for conservative field, work done along closed path is

A

zero

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8
Q

1 J is equal to how many ergs

A

10^7

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9
Q

what is the CGS unit of work

A

erg

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10
Q

for cyclic Fd graph, work done will be

A

0

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11
Q

give examples of conservative fields

A

gravitational field, electric field, magnetic field, elastic field and nuclear force

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12
Q

for non-conservative field, work done along closed path is

A

not zero

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13
Q

give examples of non-conservative field

A

frictional force, drag force, air resistance, tension and normal reaction

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14
Q

define energy

A

ability of body to do work

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15
Q

formula for potential energy

A

P.E = mgh

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16
Q

formula for absolute potential energy

A

P.E = -GMm/R

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17
Q

formula for kinetic energy

A

1/2mv^2

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18
Q

formula for elastic potential energy

A

1/2kx^2

19
Q

potential energy if movement is upwards will be

A

-mgh

20
Q

potential energy if movement is downward will be

A

+mgh

21
Q

negative P.E means

A

increasing potential energy

21
Q

positive P.E means

A

decreasing P.E

21
Q

in the presence of air resistance, what will be the formula relating P.E & K.E if movement is upward

A

K.E = P.E + Wf
1/2mv^2 = mgh + hf

22
Q

in the absence of air, what will be the formula relating P.E & K.E

A

loss in P.E = gain in P.E
mgh(h1-h2) = 1/2mv^2

23
Q

in the absence of air, what will be the formula for velocity

A

√ 2g (h1-h2)

24
Q

what is the formula relating K.E & momentum

A

K.E = p^2 / 2m

24
Q

in the presence of air resistance, what will be the formula relating P.E & K.E if movement is downward

A

P.E = K.E + Wf
mgh = 1/2mv^2 + fh

25
Q

shortcut for finding percentage change in K.E

A

% K.E = 2p + p^2/100

26
Q

define escape velocity

A

the minimum velocity which is required to throw a body outside the earth’s gravitational field is called escape velocity

27
Q

formula for escape velocity

A

v = √ 2GM/R

28
Q

on which factors escape velocity does NOT depend

A

size and mass of object
angle of projection

28
Q

what is the value of escape velocity for earth

A

11km/s

29
Q

on which factors does escape velocity depend

A

on the size and mass of planet only

30
Q

what is the work energy principle?

A

work done on a body always changes its kinetic energy

31
Q

the stopping distance d is directly proportional to

A

the square of velocity

32
Q

define power

A

the rate of doing work is called power

33
Q

formula of power for lift

A

P = mgh/T

34
Q

1 erg is equal to how many joules

A

10^-7 Joules

35
Q

SI unit of power is

A

Watt

36
Q

the famous unit of power is called

A

horsepower

37
Q

1 horsepower is equal to how many watts?

A

746 W

38
Q

1 kWh is equal to how many joules

A

3.6 x 10^6

39
Q

1 calorie is equal to how many joules

A

4.18

40
Q

1 eV is equal to how many joules

A

1.6 x 10^-19

41
Q

1 Joule is equal to how many eV

A

6.25 x 10^18 eV

42
Q

1 Joule is equal to how many ergs

A

10^7

PHYSICS (6 decks)

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