Explanation:
Work done is given by the product of force and displacement.
Case 1,
1. A boy lifts a 2-newton box 0.8 meters.
W = 2 N × 0.8 m = 1.6 J
2. A boy lifts a 5-newton box 0.8 meters.
W = 5 N × 0.8 m = 4 J
3. A boy lifts a 8-newton box 0.2 meters.
W = 8 N × 0.2 m = 1.6 J
4. A boy lifts a 10-newton box 0.2 meters.
W = 10 N × 0.2 m = 2 J
Out of the four options, in option (2) ''A boy lifts a 5-newton box 0.8 meters'', the work done is 4 J. Hence, the greatest work done is 4 J.
Answer:
Isothermal : P2 = ( P1V1 / V2 ) , work-done 
Adiabatic : : P2 =
, work-done =
W = 
Explanation:
initial temperature : T
Pressure : P
initial volume : V1
Final volume : V2
A) If expansion was isothermal calculate final pressure and work-done
we use the gas laws
= PIVI = P2V2
Hence : P2 = ( P1V1 / V2 )
work-done :

B) If the expansion was Adiabatic show the Final pressure and work-done
final pressure

where y = 5/3
hence : P2 = 
Work-done
W = 
Where 
Answer:
Friction = 5 N
Explanation:
As we know that block is moving at constant speed
So the acceleration of the block is zero
So we will have

for net force to be zero
Force exerted on the object by external system must be counter balanced by the force of friction
So we have

so we have

The answer would be D. absorption and radiation of energy in the atmosphere
Answer:
A dekagram is thousand (1000) times larger than a centigram.
Explanation:
→ [1 dekagram = 1,000 centigrams]
→ 1 dekagram = 10 grams
→ 10 grams = 100 decigrams
→ 100 decigrams = 1,000 centigrams