A ball is thrown horizontally from the top of a building 0.10 km high. The ball strikes the ground at a point 78 m horizontally
1 answer:
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(a)
The total mechanical energy of the projectile at the beginning is the sum of the initial kinetic energy (K) and potential energy (U):
The initial kinetic energy is:
where m = 58.0 kg is the mass of the projectile and is the initial speed. Substituting,
The initial potential energy is given by
where g=9.8 m/s^2 is the gravitational acceleration and h=132 m is the height of the cliff. Substituting,
So, the initial mechanical energy is
(b)
We need to calculate the total mechanical energy of the projectile when it reaches its maximum height of y=336 m, where it is travelling at a speed of v=99.2 m/s.
The kinetic energy is
while the potential energy is
So, the mechanical energy is
And the work done by friction is equal to the difference between the initial mechanical energy of the projectile, and the new mechanical energy:
And the work is negative because air friction is opposite to the direction of motion of the projectile.
(c) 88.1 m/s
The work done by air friction when the projectile goes down is one and a half times (which means 1.5 times) the work done when it is going up, so:
When the projectile hits the ground, its potential energy is zero, because the heigth is zero: h=0, U=0. So, the projectile has only kinetic energy:
E = K
The final mechanical energy of the projectile will be the mechanical energy at the point of maximum height plus the work done by friction:
And this is only kinetic energy:
So, we can solve to find the final speed:
Answer:
The value of the angle theta = 135degree, which is option c.
Explanation :
These are the options given in the question
a) 45 degrees
b)120 degrees
c)135 degrees
d)150 degrees
e) it is impossible to deliver a negative power.
The concept of work done on an object is applied here.
work = Fd
F = ma
work = mad
Work is a form of energy transferred by an object after the application of a force that act on the object. A step by step explanation is as attached below.
