A graph titled Distance as a Function of Time with horizontal axis time (seconds) and vertical axis distance (meters). A straigh
2 answers:
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Answer:
(a) There are 3.17 times more shakes in a second than seconds in a year.
(b) Humans have existed for 9067.72 universe seconds.
Explanation:
(a) First we calcule how many seconds are in a year. One year have 365 days, one day has 24 hours, one hour has 60 minutes and one minute has 60 seconds, so:
Now, we calculate how many shakes are in a second:
Finally, we calculate how many more shakes in a second are there than seconds in a year:
(b) Using a simple rule of three we can calculate how many "universe seconds" have humans existed, recall that 1 day has 86400 seconds:
1010 years--------->86400s
106 years----------> x seconds
Answer:
The momentum, ΔP, and therefore, kinetic energy given to the ball in a serve is the result of the product of the tension force, 'F', in the string and the time of contact, Δt, between the ball and the string
ΔP = F × Δt
Explanation:
The impulse, ΔP, is the produce of the force, 'F', applied to a body for a given period of time, Δt', that gives motion to the body, and it is equal to the change of momentum of the body
ΔP = F × Δt
The momentum, 'P', of a body is the product of the mass, 'm', of the body and its velocity, 'v'
P = m × v
Tension is the axial pulling force of a string
T = Axial Force, F
The tension used in Tennis Racket strings is between 40 to 65 lbs.
When high tension is used in the string, the string is taut, and the contact duration between the Racket string and the ball is minimal, and the player needs to use more force to obtain a high momentum, and therefore, energy in the ball, which reduces control, and increase stress, as force is more emphasized
When low tension is used in the string, the Tennis Racket strings are more elastic. During a serve, the ball pushes the strings further back into the racket, such that the ball spends more time in contact with the string, (Δt is larger), and therefore, the impulse, F·Δt = ΔP, given to the ball is larger, therefore, the ball has a larger change in momentum, and therefore more energy in the intended direction.
However, a very slackened string will increase the increase area and time (large Δt) of contact of the ball and the racket such that the force given to the ball, F = ΔP/(large Δt) is reduced and therefore reduce the likelihood of gaining points from a serve against an opponent with a much forceful return of a serve.