Answer:
-58.8 J
Explanation:
The work done by a force is given by:

where
F is the magnitude of the force
d is the displacement of the object
is the angle between the direction of the force and the displacement.
In this problem, we are asked to find the work done by gravity, so we must calculate the magnitude of the force of gravity first, which is equal to the weight of the object:

The displacement of the object is d = 3.00 m, while
, because the displacement is upward, while the force of gravity is downward; therefore, the work done by gravity is

And the work done is negative, because it is done against the motion of the object.
Decomposing the vector b on the x-axis and the y-axis, we get a rectangle triangle where the two sides are bx (x-axis) and by (y-axis), and b is the hypothenuse.
The component in x, bx, is equal to the product between the hypothenuse and the cosine of the angle between b and the x-axis, which is

:
Answer:
1)

2)

Explanation:
<u>Projectile Motion</u>
When an object is launched near the Earth's surface forming an angle
with the horizontal plane, it describes a well-known path called a parabola. The only force acting (neglecting the effects of the wind) is the gravity, which acts on the vertical axis.
The heigh of an object can be computed as

Where
is the initial height above the ground level,
is the vertical component of the initial velocity and t is the time
The y-component of the speed is

1) We'll find the vertical component of the initial speed since we have not enough data to compute the magnitude of 
The object will reach the maximum height when
. It allows us to compute the time to reach that point

Solving for 

Thus, the maximum heigh is

We know this value is 8 meters

Solving for 

Replacing the known values


2) We know at t=1.505 sec the ball is above Julie's head, we can compute




The formula for potential energy is PE=mgh
It can have that high of a potential energy if it's relative height what super high.
Answer:
The correct answer is c. When the balloon hits the ground, the rubber envelope stretches, storing elastic potential energy; this elastic potential energy is converted to the gravitational potentiaL
Explanation:
Let's analyze the situation of the globe
When it touches the ground, the part that is in contact decreases its velocity to zero, but the upper part of the ball continues to move, which creates that the molecules approach slightly, if we approximate the spring links, a repulsive force is created that after all the particles reach zero speed. The force of the springs moves the ball up until the force decreases to zero.
We can relate this force of Hooke with an elastic energy
This energy can be stored in the deformation of the system, as elastic potential energy, which is subsequently transformed into gravitational potential energy when the balloon is lifted.
The correct answer is c