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# A cheetah can start from rest and attain the velocity 72km/h in 2 seconds. Calculate the acceleration of cheetah

yan [13]

Answer:

Explanation:

Solution,

When a certain object comes in motion from rest, in the case, initial velocity = 0 m/s

Initial velocity ( u ) = 0 m/s

Final velocity ( v ) = 72 km/h ( Given)

We have to convert 72 km /h in m/s

$72 \: km \: per \: hour$

$= 72 \times \frac{1000}{60 \times 60}$

$= 20$ m/s

Final velocity ( v ) = 20 m/s

Time taken ( t ) = 2 seconds

Acceleration (a) = ?

Now,

we have,

$a = \frac{v - u}{t}$

$a = \frac{20 - 0}{2}$

$a = \frac{20}{2}$

$a = 10$ m/s ^2

Hope this helps...

Good luck on your assignment..

7 0

3 years ago

A system undergoes a two-step process. In the first step, the internal energy of the system increases by 222 J when 150 J of wor

joja [24]

Answer:0 J

Explanation:

Given

For first step

change in internal Energy of the system is $\Delta U_1=222 J$

Work done on the system $W_1=-150 J$

For second step

change in internal Energy of the system is $\Delta U_2=123 J$

Work done on the system $W_2=-195 J$

Work done on the system is considered as Positive and vice-versa.

and from first law of thermodynamics

$Q=\Delta U+W$

for first step

$Q_1=222-150=72 J$

$Q_2=123-195=-72 J$

overall heat added $=Q_1+Q_2$

$Q_{net}=72-72 =0$

For overall Process Heat added is 0 J

8 0

3 years ago

What does frequency describe?

ddd [48]

The whole definition of frequency is: <em>How often something happens. </em>

Especially referring to something that happens over and over and over and over.

One example is Choice-C: How often the particles of a medium vibrate.

"Frequency" comes from the word "frequent". That means "often", and "frequency" just means "often-ness" ... HOW often the thing happens.

Some other examples:

Frequency of jump-roping . . . maybe 60 per minute .

Frequency of rain . . . maybe 5 per month .

Frequency of an AM radio station . . . maybe 1 million waves per second.

(If it's something <u><em>per second</em></u>, then we call it "Hertz". That's not for the car rental company. It's for Heinrich Hertz, the German Physicist who was the first one to prove that electromagnetic waves exist. He sent radio waves all the way ACROSS HIS LABORATORY and detected them at the other side ( ! ), in 1887.)

Frequency of the wiggles in the sound wave coming out of a trumpet playing the note ' A ' . . . 440 Hertz.

Frequency of sunrise and the Chicago Tribune newspaper . . . 1 per day

Frequency of the cycle of Moon phases and an average human woman's ovulation cycle: 1 per 29.531 days, 1 per ~28 days .

7 0

3 years ago

Read 2 more answers

A factory worker pushes a 30.0-kg crate a distance of 4.5 m along a level floor at constant velocity by pushing horizontally on

SIZIF [17.4K]

(a) 73.5 N

The velocity of the crate is constant: this means that the acceleration is zero (a=0), so according to Newton's second law

$\sum F = ma$

the resultant of the forces must be zero: $\sum F = 0$ (1)

The motion is along the horizontal direction, so we are only interested in the forces acting along this direction. There are two of them:

$F$ , the push applied by the worker

$F_f=-\mu mg$ , the force of friction, with $\mu=0.25$ being the coefficient of friction, $m=30.0 kg$ being the mass of the crate, and $g=9.8 m/s^2$ . The negative sign is due to the fact that the friction acts in the opposite direction to the motion. Eq.(1) then becomes

$F-\mu mg=0\\F=\mu mg=(0.25)(30.0 kg)(9.8 m/s^2)=73.5 N$

So, this is the force that the worker must apply.

(b) 330.8 J

The work done by the pushing force of the worker on the crate is given by:

$W=Fd cos \theta$

where

F = 73.5 N is the force

d = 4.5 m is the displacement

$\theta=0^{\circ}$ is the angle between the direction of the force and the displacement (0 degrees, since they are in same direction)

Substituting, we have

$W=(73.5 N)(4.5 m)(cos 0^{\circ})=330.8 J$

(c) -330.8 J

To calculate the work done by friction, we apply the same formula:

$W=F_f d cos \theta$

where

$F_f = \mu mg=(0.25)(30.0 kg)(9.8 m/s^2)=73.5 N$ is the magnitude of the force of friction

d = 4.5 m is the displacement

$\theta=180^{\circ}$ is the angle between the direction of the force of friction and the displacement (it is 180 degrees since the two are into opposite directions)

Substituting, we find

$W=(73.5 N)(4.5 m)(cos 180^{\circ})=-330.8 J$

So, the work done by friction is negative.

(d) 0 J

As before, the work done by any force on the crate is

$W=F_f d cos \theta$

We notice that both gravity and normal force are perpendicular to the displacement: therefore, $\theta=90^{circ}$ , and so

$cos \theta=0$

which means that the work done by both forces is zero.

(e) 0 J

The total work done on the crate is the sum of the work done by the four forces acting on it, so:

$W=W_{push} + W_{friction}+W_{gravity}+W_{normal}=330.8J-330.8J+0+0=0$

And this is in accordance with the work-energy theorem, which states that the variation of kinetic energy of the crate is equal to the work done on it: since the crate is moving at constant velocity, its variation of kinetic energy is zero, as well as the work done on it.

5 0

3 years ago

A solar cooker, really a concave mirror pointed at the Sun, focuses the Sun's rays 13.8 cm in front of the mirror. Part A What i

shepuryov [24]

From the concept of optics on a curvature of a spherical mirror, the proportion for which the focal length is equivalent to half the radius of curvature is fulfilled. Mathematically this is

$f = \frac{R}{2}$

Here,

f = Focal Length

R = Radius

Rearranging to find the radius we have,

$R = 2f$

Replacing with our values,

R = 2(13.8cm)

R = 27.6cm

Therefore the radius of the spherical surface from which the mirror was made is 27.6cm

6 0

3 years ago