A rock is thrown from a height of 2.0 m at a window that is located 9.0 m above the ground. The initial velocity of the rock is 20 m/s, and it is thrown at an angle of 40 above the horizontal. If the rock strikes the window on the upward trajectory, what is the horizontal distance between the person throwing the rock and the window

The value is  

Explanation:

From the question we are told that

   The height is h =  2.0 m

   The height of the window is

    The initial velocity of the rock is

    The angle at which it is thrown is

Generally the  vertical component of the velocity of the stone is mathematically represented as

=>

Generally the height of the window from the ground is mathematically represented as using kinematic equation as

=>  

Here g is negative -9.8 m/s^2 because the direction of the stone is against gravity

   So

Solving this quadratic equation using quadratic formula we obtain

     t = 0.770 s

Generally the velocity of the stone on the x axis is mathematically represented as

=>    

Generally the distance between the person throwing the rock and the window is mathematically represented as

=>    

=>    

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.

a and c

c is 100% but i am confused in a