Chapter 6 ~ Work, Energy And Power ⛮

Question 1

Definition of work done :

Plus formula

Answer 1

°the product of the force and the distance moved in the direction of the force

W= F × s

Question 2

Work done =

Answer 2

Energy ⛮ transferred

Question 3

1 joule =

Answer 3

1 Newton × 1 m

Therefore, 1 J = 1 Nm

Question 4

The formula for work done by a gas is

Answer 4

W = p🔼V

W-work done by a gas

p-pressure (remains constant)

🔼V- change in volume

Question 5

How to derive the work done by a gas formula in 2 steps?

W= p🔼V

Answer 5

Step 1 : F = pressure × area
F = p× A

Step 2 : work done =F × s
Therefore, W = p × A × s

         W= p 🔼 V

Question 6

Definition of gravitational potential energy ⛮

And its formula

Answer 6

°the energy a body has due to its position in a gravitational field

Ep= mgh

m-mass, kg

g- gravitational force, 9.81ms^-2

h- height, m

Question 7

Definition of gravitational potential

Answer 7

The gravitational potential energy per unit mass at a point in a gravitational field

Question 8

Definition of gravitational field

Answer 8

°a region where any object with mass experiences a force

Question 9

Gravitational field strength 💪 plus formula

Answer 9

°The gravitational force experienced by an object per unit mass :

g= F/m

F-force

m-mass

Question 10

Formula for kinetic energy ⛮

Answer 10

Kinetic energy = 1/2 × mass × speed ^2

KE =0.5×m×v^2

Question 11

Definition of kinetic energy :

Answer 11

°energy of an object due to its motion

Question 12

How to derive the formula for kinetic energy in 4 steps

KE =(1/2) mv^2

Answer 12

Step 1 :
Imagine a body being accelerated from rest
The equation of motion v^2 = u^2 +2as
U = 0 (rest)

So v^2 = 2as

Step 2 :
Multiple each side by (1/2)m
So (1/2) mv^2 = mas

Step 3 :
ma = F
So mas is the force × distance moved

Step 4:

Work done by force F= (1/2)mv^2

Question 13

Decrease in g.p.e =

Answer 13

Gain in k.e.

Question 14

Decrease in g.p.e =

Answer 14

Gain in k.e.

Question 15

How to derive g.p.e in 2 steps

Answer 15

Step 1 :
Work done = F × s

Step 2 :
F = W= mg
s = displacement which changes so h

Therefore,

g.p.e = mgh

Question 16

Formula for efficiency =

Answer 16

Effiency =

(useful output energy /total input energy) × 100

Question 17

The principle of the conservative of energy is:

Answer 17

Energy ⛮ cannot be created or destroyed. It can only be converted from one form to another.

Question 18

Definition of power :

➕ Unit

Answer 18

The rate at which energy is transferred or the rate at which work is done.

Unit : Watt (W)

Question 19

Formula for power =

Answer 19

P = W/t

P- power
W-work done
t-time ⌚

Question 20

A watt is defined as

Answer 20

A rate of transfer of energy of one joule per second.

Question 21

The formula for moving power =

Answer 21

P=Force ×velocity

Question 22

How to derive the formula for moving power (P=F×v) in 3 steps :

Answer 22

Step 1 :
W= F× s
And distance (s) = v × t

Therefore, W= F × v × t

Step 2 :
P = work done ÷ time ⌚ so,

(F× v × t) /t

Step 3 :
Therefore, P= F × v