Physics, 15.01.2020 06:31 Daisysolis136

A1.5 kilogram cart initially moves at 2.0 meters per second. it is brought to rest by a constant net forcé in 3.0 second. what is the magnitude of the net force ?

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The net force on the cart is

   Force = (mass) x (acceleration) .

We know the mass = 1.5 kilogram, but we need to
calculate the acceleration.

   Acceleration = (change in speed) / (time for the change)

Change in speed = (ending speed) minus (beginning speed)

   = ( 0 ) - ( 2 m/s ) =   -2 m/s

Acceleration = (change in speed) / (time for the change)

   = ( -2 m/s ) / (3 sec)

   = - 2/3 m/s² .

Finally ...    Net force = (mass) x (acceleration)

   = (1.5 kilogram) x ( - 2/3 m/s²)

   = ( - 3/2 x 2/3 ) (kg-m/s²)

   = - 1 newton .

The negative sign on the force means the force is applied
opposite to the direction the cart is moving. That gives
negative acceleration (slowing down), and the cart
eventually stops.

Answer from: Quest

a.) travels faster in solids because the particles are closer together.

air is a gas water is a liquid

Answer from: Quest

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

$x(t)=ax(x-6)$

where $a$ is unknown. because the position is parabolic, there is symmetry about the midpoint at $t=3$ , and we know that

$x(3)=10\implies -9a=10\implies a=-\dfrac{10}9$

so that the position function is

$x(t)=-\dfrac{10}9x(x-6)$

which means the velocity is

$v(t)=\dfrac{\mathrm dx}{\mathrm dt}=-\dfrac{20}9x+\dfrac{60}9$

then the total distance traveled is

$\displaystyle\int_{t=0}^{t=6}|v(t)|\,\mathrm dt=\left\{\int_{t-0}^{t=3}-\int_{t=3}^{t=6}\right\}v(t)\,\mathrm dt=20$

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at $x=0$ and ends at $x=0$ , so its displacement is 0.

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