The hitter just hit the ball with a bat. He wants the ball to travel as straight as possible

A. In the illustration above, are the forces acting on the ball balanced or unbalanced? If unbalanced, which force is most powerful.

B. Is friction acting on the ball? If so, explain how it may change the ball’s speed and direction.

A) Unbalanced

B) Yes

Explanation:

A)

Here we are analzying the situation just after the ball has been hit by the bat.

In this situation, there are only two forces acting on the ball:

- The force of gravity, acting in the downward direction, of magnitude (where m is the mass of the ball and g the acceleration due to gravity)

- The friction due to the air (air resistance), acting in the direction opposite to the motion

As we can see, the two forces act in different directions: according to the rules of vector addition, this means that the resultant force on the ball is different from zero; therefore, the net force on the bat is unbalanced.

We can also say that the stronger force is the force of gravity (in fact, the air resistance is generally small).

B)

Yes.

As we said, apart from gravity, there is another force acting on the ball: friction (or better called air resistance).

without the presence of air resistance, the ball would follow a parabolic trajectory, due to the combination of:

- The horizontal motion, which is uniform (no forces acting in this direction)

- The vertical motion, which is accelerated (due to the presence of the constant force of gravity)

However, in real life we also have to consider the presence of the air resistance. The direction of the air resistance is opposite to the motion of the ball: as a result, it will have the following effect:

- It will decrease the speed of the ball, as the force does negative work on the ball

- It will decrease the maximum height and the range of the ball, as the ball will decrease its speed faster

d₁ = displacement of tern from arctic to antarctic = 11000 miles

d₂ = displacement of tern from antarctic to arctic =   - 11000 miles

d = total displacement for the journey

total displacement for the journey is given as

d = d₁ + d₂

d = 11000 + (-11000)

d = 0 miles

t₁ = time of travel from arctic to antarctic = 3 months = 3 x 30 days = 90 days

t₂ = time of travel from antarctic to arctic = 3 months = 3 x 30 days = 90 days

t = total time of travel

total time of travel is given as

t = t₁ + t₂

t = 90 + 90

t = 180 days

average velocity is given as

average velocity = total displacement/ total time

v = d/t

v = 0/180

v = 0 miles/day

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.