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3 years ago

True or false? objects that are sitting still have kinetic energy

1 answer:

5 0

Kinetic energy is the energy of an object due to its motion. An object sitting still isn't moving, therefore it has no kinetic energy. The statement in the question is false.

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The gravitational force,F, on a rocket at a distance,r, from the center of the earth isgiven byF=kr2wherek= 1013N·km2. (Newton·k

Brrunno [24]

Answer:

The gravitational force changing velocity is

$\frac{dF}{dt}=-8\frac{N}{s}$

Explanation:

The expression for the gravitational force is

$F=\frac{k}{r^{2}}\\\\k=10x10^{13} N*km^{2}\\\\r=10x10^{4} km\\\\V=0.4 \frac{km}{s}$

Differentiate the above equation

$\frac{dF}{dt}=\frac{k}{r^{2}}\\\frac{dF}{dt}=k*r^{-2}\\\frac{dF}{dt}=-2*k*r^{-3} \frac{dr}{dt}\\\frac{dF}{dt}=\frac{-2k}{r^{3}}\frac{dr}{dt}$

The velocity is the distance in at time so

$V=\frac{dr}{dt}=0.4 \frac{km}{s}$

$\frac{dF}{dt}=\frac{-2*k}{r^{3}}*0.4\\\frac{dF}{dt}=\frac{-8*10x^{13}N*km^{2} }{(10x10^{4}) ^{3}} \\\frac{dF}{dt}=\frac{-8x10^{12} }{1x10^{12}}$

$\frac{dF}{dt}=-8\frac{N}{s}$

8 0

3 years ago

The fire alarm goes off, and a 75 kg firefighter slides down a pole with a constant acceleration of a = 6 m/s square. What is th

Alex17521 [72]

Answer:

450N

Explanation:

Given data

Mass m= 75kg

Acceleration= 6m/s^2

From the Newtons first law, F=ma

substitute

F=75*6

F= 450N

Hence the force is 450N

3 0

3 years ago

2. If the efficiency of a device is 64 %, what is the amount of Energy lost/ wasted by this device?

Inessa05 [86]

It would be 78 becuase the 2 percent of 64 is many of energy lost

3 0

3 years ago

Suppose that on earth you can throw a ball vertically upward a distance of 1.20 m. Given that the acceleration of gravity on the

tatuchka [14]

Answer:

7.04 m

Explanation:

t = Time taken

u = Initial velocity

v = Final velocity = 0

s = Displacement on Earth = 1.2 m

a = Acceleration due to gravity on Moon = 1.67 m/s²

a = Acceleration due to gravity Earth= 9.81 m/s²

Accelration going up is considered as negetive

Initial Velocity of the ball

$v^2-u^2=2as\\\Rightarrow -u^2=2as-v^2\\\Rightarrow -u^2=2\times -9.81\times 1.2-0^2\\\Rightarrow u=\sqrt{2\times 9.81\times 1.2}\\\Rightarrow u=4.85\ m/s$

Assuming that the ball is thrown with the same velocity on the Moon, displacement of the ball is

$v^2-u^2=2as\\\Rightarrow s=\frac{v^2-u^2}{2a}\\\Rightarrow s=\frac{0^2-4.85^2}{2\times -1.67}\\\Rightarrow s=7.04\ m$

The displacement of the ball on the moon is 7.04 m

6 0

3 years ago

Describe liquids and GASSES IN TERMS OF THERE VOLUME AND SHAPES

antiseptic1488 [7]

Answer:

Explanation:

liquids have definite volume

liquids do not have definite shape. The take the shape of the container in which they are kept.

gases do not have definite volume.

gases do not have definite shape. They take the shape of the container in which they are kept.

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3 0

3 years ago

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