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3 years ago

8

Prehistory can be described as _____.

1 answer:

user100 [1]3 years ago

6 0

The in-between period of time when the first man appeared and when man developed a writing system. Or the period of time before man became literate.

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A particle has ~r(0) = (4 m) ˆ and ~v(0) = (2 m/s)ˆı. If its acceleration is constant and given by ~a = −(2 m/s 2 ) (ˆı +ˆ), a

Troyanec [42]

The particle has $\vec r(0)=(4\,\mathrm m)\,\vec\imath$ and $\vec v(0)=\left(2\frac{\rm m}{\rm s}\right)\,\vec\imath$ , and is undergoing a constant acceleration of $\vec a=-\left(2\frac{\rm m}{\mathrm s^2}\right)(\vec\imath+\vec\jmath)$ .

This means its position at time $t$ is given by the vector function,

$\vec r(t)=\vec r(0)+\vec v(0)t+\dfrac12\vec a t^2$

$\implies\vec r(t)=\left[4\,\mathrm m+\left(2\dfrac{\rm m}{\rm s}\right)t-\left(1\dfrac{\rm m}{\mathrm s^2}\right)t^2\right]\,\vec\imath-\left(1\dfrac{\rm m}{\mathrm s^2}\right)t^2\,\vec\jmath$

The particle crosses the x-axis when the $\vec\imath$ component is 0 for some time $t>0$ , so we solve:

$4+2t-t^2=0\implies t^2-2t+1=5$

$\implies(t-1)^2=5$

$\implies t-1=\pm\sqrt5$

$\implies t=1\pm\sqrt5$

The negative square root introduces a negative solution that we throw out, leaving us with $\boxed{t=1+\sqrt5}$ or about 3.24 seconds after it starts moving.

3 0

4 years ago

The Kinetic energy, K, of an object with mass m moving with velocity v can be found using the formula - E_{\text{k}}={\tfrac {1}

tester [92]

Answer:

The ratio of kinetic energies of 5 kg object to 20 kg object is 1:1.

Explanation:

Kinetic energy is defined as energy possessed by an object due to its motion.It is calculated by:

$K.E=\frac{1}{2}mv^2$

Kinetic energy of the 5 kg object.

Mass of object,m = 5 kg

Velocity of an object = v

$K.E=\frac{1}{2}mv^2=\frac{1}{2}\times 5kg\times v^2$

Kinetic energy of the 20 kg object.

Mass of object,m' = 20 kg

Velocity of an object = v'

$K.E=\frac{1}{2}mv^2=\frac{1}{2}\times 20kg\times v'^2$

The ratio of the kinetic energy of the 5 kilogram object to the kinetic energy of the 20-kilogram object:

$\frac{K.E}{K.E'}=\frac{\frac{1}{2}\times 5kg\times v^2}{\frac{1}{2}\times 20kg\times v'^2}$

Given that, v = 2v'

$\frac{K.E}{K.E'}=\frac{1}{1}$

The ratio of kinetic energies of 5 kg object to 20 kg object is 1:1.

3 0

3 years ago

A car with a velocity of 6.4 m/s, forward, accelerates to a velocity of 10.6 m/s, forward, in 16 s. What is the card acceleratio

tatuchka [14]

Answer:

acceleration = 0.2625 m/s²

Explanation:

acceleration = ( final velocity - initial velocity ) / time

Here the final velocity is 10.6 m/s and initial velocity is 6.4 m/s and time is 16 s.

using the equation:

acceleration = ( 10.6 - 6.4 ) / 16

= 0.2625 m/s²

6 0

3 years ago

Read 2 more answers

There is a filing cabinent that is 52 in. tall and 15 in. wide. The center of gravity of the cabinet is right at the center. To

erastova [34]

Answer:

16 degrees

Explanation:

The tipping point of the cabinet is sketched below.

5 0

2 years ago

Rearranged the equation d=10 v=2.5 for t

eimsori [14]

The time of motion of the object at the given speed and distance is 4 seconds.

<h3>Time of motion of the object</h3>

The time of motion of the object is calculated as follows;

t = d/v

where;

d is distance = 10 m
v is speed = 2.5 m/s
t is time of motion

t = 10/2.5

t = 4 s

Thus, the time of motion of the object at the given speed and distance is 4 seconds.

Learn more about time here: brainly.com/question/2854969

#SPJ1

5 0

2 years ago