4. A car accelerating at 60 meters/second is hit in an accident by a bus. The net force exerted on

A ball thrown vertically upward is caught by the thrower after 2.00 s. Find (a) the initial velocity of the ball and (b) the max

ankoles [38]

Answer:

a) 9.8 m/s

b) 4.9 m

Explanation:

This problem is a good example of Vertical motion, where the main equations for this situation are:

$y=y_{o}+V_{o}t-\frac{1}{2}gt^{2}$ (1)

$V^{2}={V_{o}}^{2}-2gy$ (2)

Where:

$y$ is the height of the ball at a given time

$y_{o}=0m$ is the initial height of the ball (assuming the hand of the thrower the origin of the system)

$V_{o}$ is the initial velocity of the ball

$V$ is the final velocity of the ball

$t=2s$ is the time it takes for the ball to make the complete movement (from the moment it is thrown until it falls back into the pitcher's hands)

$g=9.8 m/s^{2}$ is the acceleration due to gravity

Knowing this, let's begin with the answers:

<h3>a) Initial velocity </h3>

In order to find the initial velocity $V_{o}$ of the ball, we will use equation (1) and $t=2s$ , taking into account that $y=0 m$ and $y_{o}=0m$ at this given time:

$0=0+V_{o}t-\frac{1}{2}gt^{2}$ (3)

Isolating $V_{o}$ :

$V_{o}=\frac{1}{2}gt$ (4)

$V_{o}=\frac{1}{2}(9.8 m/s^{2})(2 s)$ (5)

Then:

$V_{o}=9.8 m/s$ (6)

<h3>b) Maximum height </h3>

In this part, we will use equation (2), knowing the value of the height is maximum when $V=0$ . So, we will name this height as $y_{max}$ :

$0={V_{o}}^{2}-2gy_{max}$ (7)

Isolating $y_{max}$ :

$y_{max}=\frac{{V_{o}}^{2}}{2g}$ (8)

$y_{max}=\frac{{(9.8 m/s)}^{2}}{2(9.8 m/s^{2})}$ (9)

Finally:

$y_{max}=4.9 m$

4 0

4 years ago

A truck moving at 45 m/s passes a police car moving at 36 m/s in the opposite direction. if the frequency of the siren is 500 Hz

elena-14-01-66 [18.8K]

Answer: observed frequency (f') = 511.97Hz

Explanation: when there is a relative motion between an observer and a sound source, the frequency of sound wave perceived by the observer is different from the frequency of originally sent out by the sound source.

This is called Doppler effect and given mathematically below as

f' = (v + v') /(v- vs) * f

f' = observed frequency

v = speed of sound in air = 340m/s

v' = velocity of observer= 45m/s

vs = velocity of source relative to observer = - 36m/s ( the negative sign came as a result of the fact that the velocity of the source is in opposite direction to the velocity of the observer)

f = original frequency of sound source = 500Hz

f' = (340 + 45)/{340 -(-36)} * 500

f' = 385/ (340 + 36) * 500

f' = 385/ 376 * 500

f' = 1.0239 * 500

f' = 511.97Hz

7 0

3 years ago

Define the focus of a concave lens

Sophie [7]

Answer:

Principal focus of concave lens - 

★ The point at which rays parallel to principal axis coming from infinity appear to converge after being refracted from concave lens is called the principal focus of concave lens.

________________________

• Additional information - 

★ Principal focus - A number of rays parallel to the principal axis after reflection from a concave mirror meet at a point on the principal axis or appear to come from a point after reflection from a convex mirror on the principal axis. This is called principal focus.

8 0

3 years ago

I don't understand any of this please help !

OlgaM077 [116]

You can see what is the electron configuration by looking at the layout of the periodic tables. the first shell will have a max of 2 electrons on it, once the first one is filled up a second is added with a max of 8 electrons on it and so on with the 8 as a max. so He, and H will only have them on the first shell but every horizontal row is a new valence or outer shell. so lets say for carbon look at the number in the upper left corner of the box will tell you the total number of electrons you will need. so start off with the first two electrons on the first shell. now you know that carbon needs 6 electrons in total, since you can only have a max of 2 on the first shell you need a second one so on the second one you will have to have the remaining 4. now elements are most stable when they have a full valence shell becuase those are the only electrons that will react with others. so if carbon has 4 it wants to either gain or lose 4 electrons so you could say that it would bond with 4H since each H will donate 1 electron to the C valence shell making all the H and C stable. CH4(methane)

6 0

3 years ago

Why electrons flow in a wire when connected to a battery?

vesna_86 [32]

Answer:

The metal atoms in the wire can't move, but their outer electrons can. The force pushes those electrons and they move to further parts of the wire, trying to reach the other end. As the electrons move away, new electrons flow into the wire through the battery to take their place.

Explanation:

6 0

3 years ago