Answer:
The initial velocity is 50 m/s.
(C) is correct option.
Explanation:
Given that,
Time = 10 sec
For first half,
We need to calculate the height
Using equation of motion

....(I)
For second half,
We need to calculate the time
Using equation of motion



Put the value of h from equation (I)


According to question,


Put the value of t₁ and t₂



Here, g = 10
The initial velocity is


Hence, The initial velocity is 50 m/s.
The amount of energy needed is 2093 J
Explanation:
The amount of energy needed to increase the temperature of a substance by
is given by the equation

where
m is the mass of the substance
C is its specific heat capacity
is the increase in temperature
For the water in this problem, we have
m = 50.0 g = 0.050 kg
(specific heat capacity of water)

Therefore, the amount of energy needed is

Learn more about specific heat capacity:
brainly.com/question/3032746
brainly.com/question/4759369
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Answer
D.Diffraction
Explanation
Diffraction is a property that is experienced by waves when they come across a barrier when they are in motion.
The ways tends to curve behind the barrier. This is called diffraction of waves.
Now, sound is a wave and it also experience diffraction. . So the brother will be able to hear the sound due to diffraction
Gravitational potential energy can be calculated using the formula <span>PE = m × g × h, where g is the gravitational acceleration and is constant hence the energy is dependent directly to mass and the height of the object. Hence more PE is registered when the object is heavier and/or at greater initial height. </span>
I think it's the letter Did (this has to be 20 characters long) it would be Different or would be D