Question

fast fast fast fast ​

Answer 1

Answer:

1) The work done by the force is zero when the force acts right angle to the direction of the motion.

2) When the force acting on the body and its displacement are in same direction, positive work is done. When the force acting on the body and its displacement are in opposite direction, negative work is done. When the force is acting on the body but its displacement is 0, work done is 0.

3)

a) Work done by swimmer on water is positive and also work done by water on swimmer.

b) Work done by any force is given by dot product of force and displacement of the particle.

So W=F.S

Where F,S are vector quantities and W is scaler quantity.

SI Unit of work done is N.m and also called Joule(J).

So work done in above case is W=FSCosθ, here θ=90

Because person moves horizontal and force of gravity is vertical.

So work done is Zero

c) Even though the man exerts force on the wall , the wall does not move. Work done = force applied displacement and since the displacement of the wall is zero. , work done is also zero.

d) When the person is climbing up the stairs, he is applying force in downward direction and the normal reaction force is in the upward direction. Here the displacement is also in the upward direction. Hence the normal reaction and displacement is in the same direction, that means work done by the force is positive.

4) The three factors are; - The mass of an object. - Acceleration due to gravity. - Height above the ground.

5) Initial Velocity, u=54km/hr=15m/s

Final velocity , v=72km/hr=20m/s

Mass =1500kg

Initial kinetic energy

2

1

mu

2

⇒

2

1

1500×15×15=168750J

Final kinetic energy

2

1

mv

2

⇒

2

1

1500×20×20=300000J

So, change in kinetic energy = work done=300000−168750=131250J

6) Ep= mgh

m x g x h

5 x 9.8 x 80

=3920 J

7) the law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be conserved over .

Explanation:

hope it helps!