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sveticcg [70]
3 years ago
8

A rock is thrown straight down at 7.2 m/s off a bridge that is 45 m above the ground. Find the

Physics
1 answer:
iragen [17]3 years ago
5 0

The rock's height <em>y</em> at time <em>t</em> is given by

<em>y</em> = 45 m + (7.2 m/s) <em>t</em> - 1/2 <em>g</em> <em>t </em>²

where <em>g</em> = 9.80 m/s² is the magnitude of the acceleration due to gravity. Set <em>y</em> = 0 and solve for <em>t</em> :

0 = 45 m + (7.2 m/s) <em>t</em> - 1/2 <em>g</em> <em>t </em>²   →   <em>t</em> ≈ 3.9 s

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An internal explosion breaks an object, initially at rest, into two pieces: A and B. Piece A has 1.9 times the mass of piece B.
Helen [10]

Kinetic energy of pieces A and B are 2724 Joule and 5176 Joule respectively.

<h3>What is the relation between the masses of A and B?</h3>
  • Let mass of piece A = Ma

Mass of piece B = Mb

  • Velocities of pieces A and B are Va and Vb respectively.
  • As per conservation of momentum,

Ma×Va = Mb×Vb

  • Here, Ma=1.9Mb

So, 1.9Mb × Va = Mb×Vb

=> 1.9Va = Vb

<h3>What are the kinetic energy of piece A and B?</h3>
  • Expression of kinetic energy of piece A = 1/2 × Ma × Va²
  • Kinetic energy of piece B = 1/2 × Mb × Vb²
  • Total kinetic energy= 7900J

=>1/2 × Ma × Va² + 1/2 × Mb × Vb² = 7900

=> 1/2 × Ma × Va² + 1/2 × (Ma/1.9) × (1.9Va)² = 7900

=> 1/2 × Ma × Va² ×(1+1.9) = 7900 j

=> 1/2 × Ma × Va² = 7900/2.9 = 2724 Joule

  • Kinetic energy of piece B = 7900 - 2724 = 5176 Joule

Thus, we can conclude that the kinetic energy of piece A and B are 2724 Joule and 5176 Joule respectively.

Learn more about the kinetic energy here:

brainly.com/question/25959744

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5 0
1 year ago
Explain why engineers leave a gap in a concrete bridge (answer must relate to density)
seraphim [82]
<span>Different materials expand and contract at different rates based on temperature. Just like if you leave a plastic bottle full of water in a freezer it will burst, but if you leave it partially full no problem.....Ok?Expansion joints do the same for bridges. There is a gap to allow for temperature related expansions and contractions. Sometimes you drive over bridges and roadways where this movement is constricted and you might notice a bumpy ride. Engineers can predict the variation of structural length based on span lengths and leave the necessary gaps.....btw, NICE QUESTION:)</span>


6 0
3 years ago
In which direction does a bag at rest move when a force of 20 newtons is applied from the right? A. in the direction of the appl
-Dominant- [34]

The correct answer is A. In the direction of applied force. This is because acceleration occurs n the direction of applied force according to Newtons second law of motion which states that the acceleration of a body is directly proportional to the applied force and takes place in the direction of force.

5 0
3 years ago
Read 2 more answers
Calculate the energy used by a radio of power 30W in 1 minute.
Alekssandra [29.7K]

Answer:

<u>1.8kJ</u>

Explanation:

Formula :

<u>Energy used = Power x time</u>

<u />

===============================================================

Given :

⇒ Power = 30 W

⇒ Time = 1 minute = 60 seconds

=============================================================

Solving :

⇒ Energy used = 30 W × 60 s

⇒ Energy used = 1,800 J

⇒ Energy used = <u>1.8kJ</u>

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2 years ago
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Why is honesty especially important in a scientist when the results of an experiment go against predictions❓❔
kramer
Because other scientists and science in general rely on their collegues' research which in turn allows development of our knowledge on the given subject. The more dont-to-earth reason may be safety. If someone performs an experiment without knowledge of its true results it might result in some danger to the safety of those perforning it without knowledge of all the risks.
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