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alukav5142 [94]

3 years ago

7

True or false—If a rock is thrown into the air, the increase in the height would increase the rock’s kinetic energy, and then th

e increase in the velocity as it falls to the ground would increase its potential energy.

1 answer:

nlexa [21]3 years ago

5 0

I think that this is false but I am not sure

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A pencil rolls horizontally of a 1 meter high desk and lands .25 meters from the base of the desk. How fast was the pencil rolli

vovikov84 [41]

Answer: 0.55 m/s

Explanation:

This situation is related to projectile motion (also called parabolic motion), where the main equations are as follows:

$x=V_{o} cos\theta t$ (1)

$y=y_{o}+Vo sin \theta t + \frac{g}{2}t^{2}$ (2)

Where:

$x=0.25 m$ is the horizontal displacement of the pencil

$V_{o}$ is the pencil's initial velocity

$\theta=0\°$ since we are told the pencil rolls <u>horizontally</u> before falling

$t$ is the time since the pencil falls until it hits the ground

$y_{o}=1 m$ is the initial height of the pencil

$y=0$ is the final height of the pencil (when it finally hits the ground)

$g=-9.8m/s^{2}$ is the acceleration due gravity, always acting vertically downwards

Begining with (1):

$x=V_{o} cos(0\°) t$ (3)

$x=V_{o}t$ (4)

Finding $t$ from (2):

$0=1 m+ \frac{-9.8m/s^{2}}{2}t^{2}$ (5)

$t=\sqrt{\frac{-2y_{o}}{g}}$ (6)

Substituting (6) in (4):

$x=V_{o}\sqrt{\frac{-2y_{o}}{g}}$ (7)

Isolating $V_{o}$ :

$V_{o}=\frac{x}{\sqrt{\frac{-2y_{o}}{g}}}$ (8)

$V_{o}=\frac{0.25 m}{\sqrt{\frac{-2(1 m)}{-9.8m/s^{2}}}}$ (9)

Finally:

$V_{o}=0.55 m/s$

4 0

4 years ago

What is the reaction force to a foot pushing down on the floor?

Helga [31]

Answer:

C. The floor pushing back against the foot

Explanation:

5 0

3 years ago

Read 2 more answers

A plane drops a rubber raft to the survivors of a shipwreck. The plane is flying at a height of 1960 m and with a speed of 109 m

Korolek [52]

In this case the rubber raft has horizontal and vertical motion.

Considering vertical motion first.

We have displacement $s = ut +\frac{1}{2}at^2$ , u = Initial velocity, t = time taken, a = acceleration.

In vertical motion

s = 1960 m, u = 0 m/s, a = 9.81 $m/s^2$

$1960 = 0*t+\frac{1}{2} *9.81*t^2\\ \\ t = 20 seconds$

So raft will take 20 seconds to reach ground.

Now considering horizontal motion of raft

u = 109 m/s, t = 20 s, a = 0 $m/s^2$

So $s = 109*20+\frac{1}{2} *0*20^2 = 2180 m$

So shipwreck was 2180 meter far away from the plane when the raft was dropped.

8 0

3 years ago

7. A child of mass m starts from rest and slides without friction from a height h along a curved waterslide (Fig. P5.46). She is

marissa [1.9K]

The mechanical energy of the girl will be conserved because the system is isolated and the initial potential energy will be equal to final kinetic energy.

<h3>What is the law of conservation of energy?</h3>

The law of conservation of energy states that energy can neither be created nor destroyed but can be transformed from one form to another.

The change in the potential energy of the launched from a height into the pool without friction from the given height h is calculated by applying the following kinematic equation.

ΔP.E = ΔK.E

where;

ΔP.E is change in potential energy of the child
ΔK.E is change in the kinetic energy of the child

mghf - mghi = ¹/₂mv² - ¹/₂mu²

where;

m is the mass of the girl
g is acceleration due to gravity
hi is the initial height of the girl
hf is the final height when she is launched into the pool
u is the initial velocity
v is the final velocity of the girl

Thus, for every closed or isolated system such as this case, mechanical energy is always conserved because the initial potential energy of the girl will be converted into her final kinetic energy.

Learn more about conservation of mechanical energy here: brainly.com/question/332163

#SPJ1

4 0

1 year ago

Earth is the only planet able to support what

saw5 [17]

Life... obviously lol

8 0

4 years ago

Read 2 more answers