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3 years ago

8

Suppose a cyclist travels 15 kilometers during the first hour. Then the cyclist travels 33 kilometers during the next 2 hours. W

hat is the cyclist's average speed?

1 answer:

Natasha2012 [34]3 years ago

7 0

Average speed = (total distance) / (total time to cover the distance)

   = (15 km + 33 km) / (1 hr + 2 hrs)

   = (48 km) / (3 hrs)

   = (48/3) km/hr

   =    16 km/hr .

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A 20 g ball is fired horizontally with speed v0 toward a 100 g ball hanging motionless from a 1.0-m-long string. The balls un-de

sladkih [1.3K]

Answer:7.93 m/s

Explanation:

Given

mass of ball $m_1=20\ gm$

Mass of hanging ball $m_2=100\ gm$

Length of string $L=1\ m$

Maximum angle turned $\theta _{max}=50^{\circ}$

$v_o$ is the initial velocity of ball 1 and 0 is the initial velocity of ball 2

For Perfectly elastic final velocity of ball 1 and 2 is given by

$v_2'=\frac{2m_1}{m_1+m_2}\cdot v_1-\frac{m_1-m_2}{m_1+m_2}\cdot v_2$

$v_1'=\frac{m_1-m_2}{m_1+m_2}\cdot v_1+\frac{2m_2}{m_1+m_2}\cdot v_2$

where $v_1$ and $v_2$ are the velocity of 1 and 2 before collision

thus $v_2'=\frac{2\times 20}{120}v_0-0$

$v_2'=\frac{v_o}{3}$

$v_1'=\frac{20-100}{120}\times v_o+0$

$v_1'=-\frac{2}{3}v_o$

By energy conservation on second ball we get

Kinetic energy=Potential Energy

$\frac{1}{2}m_2(v_2')^2=m_2gL(1-\cos \theta )$

$v_2'=\sqrt{2gl(1-\cos \theta )}$

$v_2'=\sqrt{2\times 9.8\times 1(1-0.642)}$

$v_2'=2.64\ m/s$

thus $v_o=3\times v_2'=7.93\ m/s$

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3 years ago

ccording to the law of inertia, if you see an object in motion slowing down, what can you conclude? a. That there must be some e

ivanzaharov [21]

Answer:

a)

Explanation:

Newton's First law (aka law of inertia) says that any object, not subject to an external influence, must be keep in its present motion status (at rest or moving at constant speed along a straight line) forever.

So, if we see an object in motion slowing down, there must be an external infuence acting on it, that makes it slow down, like a friction force, for instance.

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3 years ago

Question 7 of 25

gogolik [260]

$\large \mathfrak{Answer : }$

The S.I unit of velocity is m/s and since it's velocity it needs to be in a particular direction, therefore most appropriate answer is :

B. She is running west at 2.4 m/s

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3 years ago

Which of the following is an ionic compound?

const2013 [10]

compound is covalent! The bond between HI is a polar covalent bond. ... It is because Hydrogen is electropositive in nature in comparison to Iodine.

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3 years ago

A centrifuge in a medical laboratory rotates at an angular speed of 3,650 rev/min. when switched off, it rotates through 48.0 re

AlladinOne [14]

First of all we need to convert everything into SI units.

Let's start with the initial angular speed, $\omega _i = 3650 rev/min$ . Keeping in mind that
$1 rev = 2 \pi rad$
$1 min=60 s$
we have
$\omega _i = 3650 \frac{rev}{min} \cdot \frac{2 \pi rad/rev}{60 s/min} =382.0 rad/s$

And we should also convert the angle covered by the centrifuge:
$\theta = 48.0 rev= 48.0 rev \cdot 2 \pi \frac{rad}{rev}=301.4 rad$

This is the angle covered by the centrifuge before it stops, so its final angular speed is $\omega_f =0$ .

To solve the problem we can use the equivalent of
$2aS = v_f^2 -v_i^2$
of an uniformly accelerated motion but for a rotational motion. It will be
$2 \alpha \theta = \omega_f^2-\omega_i^2$
And by substituting the numbers, we can find the value of $\alpha$ , the angular acceleration:
$\alpha=- \frac{\omega_i^2}{2 \theta}=- \frac{(382 rad/s)^2}{2 \cdot 301.4 rad}=-242.1 rad/s^2$

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3 years ago