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4 years ago

What is a common ancestor

Physics

1 answer:

RSB [31]4 years ago

8 0

Answer:

Common descent describes how, in evolutionary biology, a group of organisms share a most recent common ancestor. There is massive evidence of common descent of all life on Earth from the last universal common ancestor

Explanation:

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Cars A and B are racing each other along the same straight road in the following manner: Car A has a head start and is a distanc

4vir4ik [10]

The question is incomplete. Here is the complete question.

Cars A nad B are racing each other along the same straight road in the following manner: Car A has a head start and is a distance $D_{A}$ beyond the starting line at t = 0. The starting line is at x = 0. Car A travels at a constant speed $v_{A}$ . Car B starts at the starting line but has a better engine than Car A and thus Car B travels at a constant speed $v_{B}$ , which is greater than $v_{A}$ .

Part A: How long after Car B started the race will Car B catch up with Car A? Express the time in terms of given quantities.

Part B: How far from Car B's starting line will the cars be when Car B passes Car A? Express your answer in terms of known quantities.

Answer: Part A: $t=\frac{D_{A}}{v_{B}-v_{A}}$

Part B: $x_{B}=\frac{v_{B}D_{A}}{v_{B}-v_{A}}$

Explanation: First, let's write an equation of motion for each car.

Both cars travels with constant speed. So, they are an uniform rectilinear motion and its position equation is of the form:

$x=x_{0}+vt$

where

$x_{0}$ is initial position

v is velocity

t is time

Car A started the race at a distance. So at t = 0, initial position is $D_{A}$ .

The equation will be:

$x_{A}=D_{A}+v_{A}t$

Car B started at the starting line. So, its equation is

$x_{B}=v_{B}t$

Part A: When they meet, both car are at "the same position":

$D_{A}+v_{A}t=v_{B}t$

$v_{B}t-v_{A}t=D_{A}$

$t(v_{B}-v_{A})=D_{A}$

$t=\frac{D_{A}}{v_{B}-v_{A}}$

Car B meet with Car A after $t=\frac{D_{A}}{v_{B}-v_{A}}$ units of time.

Part B: With the meeting time, we can determine the position they will be:

$x_{B}=v_{B}(\frac{D_{A}}{v_{B}-v_{A}} )$

$x_{B}=\frac{v_{B}D_{A}}{v_{B}-v_{A}}$

Since Car B started at the starting line, the distance Car B will be when it passes Car A is $x_{B}=\frac{v_{B}D_{A}}{v_{B}-v_{A}}$ units of distance.

5 0

3 years ago

Describle the path that moisture takes from the ocean to the runoff that forms a river

Sergeu [11.5K]

The path that moisture takes from the ocean to the runoff that forms a river is:
1.Evaporation (water changes from a liquid to a gas or vapor)
2. Condensation (clouds are formed)
3. Precipitation (Any form of water that falls to the Earth's surface from the clouds)

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3 years ago

Marybeth and Grant are pushing on a wagon, both pushing in opposite directions. Marybeth is pushing to the left with a force of

Vladimir [108]

Answer:

14 N to the right

Explanation:

The net force is equal to the resultant of the forces acting on the wagon. In this case, we are considering two forces acting on the wagon:

- The force applied by Marybeth, to the left, of magnitude 34 N

- The force applied by Grant, to the right, of magnitude 48 N

Since the two forces are in opposite directions, in order to find the net force, we must choose a positive direction. Let's take "right" as positive direction, so the net force is:

$F=+48 N-34 N=+14 N$

And the positive sign means the net force is to the right. Due to this net force different from zero, the wagon will have an acceleration to the right, so if the wagon was at rest, it will start moving to the right.

4 0

3 years ago

A reasonable walking speed is _____. A. 0.02 m/s B. 0.2 m/s C. 2 m/s D. 20 m/s

statuscvo [17]

I am gonna have to say A 0.02 because 2 meters a second is way too fast 0.2 is a little more than reasonable and if 2 meters a second is too fast then 20 is off so A. should be most reasonable

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4 years ago

A swimmer wants to swim straight across a river with current flowing at a speed of v1 = 0.32 km/h. If the swimmer swims in still

yawa3891 [41]

For the swimmer to go straight the sin component of his velocity should cancel the river velocity.

So, we have $v_{1} = v_2sin$ θ