Select True or False for each statement. 1 Work cannot be done in the absence of
ID: 1261353 • Letter: S
Question
Select True or False for each statement.
1 Work cannot be done in the absence of motion.
2 Work is done when the form of energy changes.
3 Without friction or work by an external force, the sum of the potential and kinetic energies of a body is constant.
4 Energy conservation law for a projectile (no friction): Potential energy increase equals the kinetic energy decrease.
5. A source of energy is required to do work.
6. More power is required while slowly lifting a box than while lifting it up quickly.
Explanation / Answer
1. True
Work done = F.d
if there is no motion then d (displacement ) will be zero so work done = 0
2. True ( work - enetgy relation)
3. False
work done by internal force can change its energy .
E.g - When bomb blasts in parts.
4. True.
from work - energ theorem.
work done by gravity = change in K.E.
increase in potential energy ( means negative work done by gravity ) = loss in K.E.
5. True
from work - energy theorem.
work done = change in energy
6. False
Power = work / time
same work done quickly, then time will be less .
ao powerr will be more.
power is less in slowly lifting.