<span>x=((12.3/100)m)cos[(1.26s^−1)t]
v= dx/dt = -</span><span>((12.3/100)*1.26)sin[(1.26s^−1)t]
v=</span>-((12.3/100)*1.26)sin[(1.26s^−1)t]=-((12.3/100)*1.26)sin[(1.26s^−1)*(0.815)]
v=<span>
<span>-0.13261622 m/s
</span></span>the object moving at 0.13 m/s <span>at time t=0.815 s</span>
The force of F=10 N produces an extension of

on the string, so the spring constant is equal to

Then the string is stretched by

. The work done to stretch the string by this distance is equal to the variation of elastic potential energy of the string with respect to its equilibrium position:
PART A)
horizontal distance that will be moved = 14 m
Height of the fence = 5.0 m
height from which it is thrown = 1.60 m
angle of projection = 54 degree
So here we can say that stone will travel vertically up by distance

now we will have displacement in horizontal direction

now we know that


now we will have


also for y direction


now from the two equations we will have




now from above equations


So the minimum speed will be 13.2 m/s
Part B)
Total time of the motion after which it will land on the ground will be "t"
so its vertical displacement will be

now we will have




Now the time after which it will reach the fence will be t1 = 1.8 s
so total time after which it will fall on other side of fence


now the displacement on the other side is given as



Answer:
A) 12P
Explanation:
The power produced by a force is given by the equation

where
W is the work done by the force
T is the time in which the work is done
At the beginning in this problem, we have:
W = work done by the force
T = time taken
So the power produced is

Later, the force does six times more work, so the work done now is

And this work is done in half the time, so the new time is

Substituting into the equation of the power, we find the new power produced:

So, 12 times more power.
Answer:D
Explanation:
Given
mass of object 
Distance traveled 
velocity acquired 
conserving Energy at the moment when object start falling and when it gains 12 m/s velocity
Initial Energy
Final Energy

where
is friction work if any


Since Friction is Present therefore it is a case of Open system and net external Force is zero
An open system is a system where exchange of energy and mass is allowed and Friction is acting on the object shows that system is Open .