(a) The work done by the bird to raise the snake on the branch is equal to the product between the weight of the snake and the height of the branch above the ground:

where
is the mass of the snake and
is the height of the branch with respect to the ground. Substituting numbers into the equation, we find

(b) The work the bird did to raise its own centre of mass from the ground to the branch is equal to the product between the bird's weight and the height of the branch:

where
is the mass of the bird. Substituting numbers into the equation, we find

The average speed will be:
Total distance travelled divided by time taken
Total distance (in metres)= 80+125+45=250
Total time (minutes) =10
250/10
=25
Thus Mary's average speed is 25 metres per minute.
Answer:
Force, F = 2356.19 N
Explanation:
Given that,
Diameter of the circular tip, d = 1 mm = 0.001 m
Its radius, r = 0.0005 m
Pressure created, 
To find,
Force exerted on the nail.
Solution,
The pressure exerted by an object is equal to the force acting per unit area. Its formula is given by :



F = 2356.19 N
Therefore, the force exerted on the nail is 2356.19 N.
Answer:
As one goes "forward" in time, the second law of thermodynamics says, the entropy of an isolated system can increase, but not decrease. ... Thus, entropy measurement is a way of distinguishing the past from the future.
Explanation: