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2 years ago

A ball starts at rest and rolls down an inclined plane. The ball reaches 7.5 m/s in 3 seconds. What is the acceleration?

Physics

1 answer:

just olya [345]2 years ago

7 0

Answer:

$a=2.5\ m/s^2$

Explanation:

<u>Motion With Constant Acceleration </u>

It's a type of motion in which the velocity of an object changes uniformly over time.

The equation that describes the change of velocities is:

$v_f=v_o+at$

Where:

a = acceleration

vo = initial speed

vf = final speed

t = time

Solving the equation for a:

$\displaystyle a=\frac{v_f-v_o}{t}$

The ball starts at rest (vo=0) and rolls down an inclined plane that makes it reach a speed of vf=7.5 m/s in t=3 seconds.

The acceleration is:

$\displaystyle a=\frac{7.5-0}{3}$

$\boxed{a=2.5\ m/s^2}$

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A boy whirls a ball on a string in a horizontal circle of radius 1 m. How many revolutions per minute must the ball make if its

spayn [35]

Answer:

Nearest, the revolutions per minute will be 29.

Explanation:

Given that,

Radius of circle = 1 m

Acceleration a =g

We know that,

Angular frequency is defined as,

$\omega=2\pi n$

Where, n = number of revolutions in one second

We need to calculate the revolutions in one second

Using formula of centripetal acceleration

$a=\omega^2r$

Put the value of a and ω

$g=(2\pi n)^2r$

$n=\sqrt{\dfrac{g}{r}}\times\dfrac{1}{2\pi}$

Put the value into the formula

$n=\sqrt{\dfrac{9.8}{1}}\times\dfrac{1}{2\pi}$

$n=0.49$

We need to calculate the revolutions per minute

Using value for the revolutions per minute

$n=0.49\times60$

$n=29.4$

Hence, Nearest, the revolutions per minute will be 29.

7 0

2 years ago

An electron has a kinetic energy of 3.00 ev. find its wavelength. (b) what if? a photon has energy 3.00 ev. find its wavelength.

Harman [31]

(a) The electron kinetic energy is
$K=3.00 eV$
which can be converted into Joule by keeping in mind that
$1 eV=1.6 \cdot 10^{-19}eV$
So that we find
$K=3.00 eV \cdot 1.6 \cdot 10^{-19} eV/J =4.8 \cdot 10^{-19}J$

The kinetic energy of the electron is related to its momentum p by:
$K= \frac{p^2}{2m}$
where m is the electron mass. Re-arranging the equation, we find
$p= \sqrt{ 2Km}= \sqrt{ 2 ( 4.8 \cdot 10^{-19} J)(9.1 \cdot 10^{-31} kg) } =9.35 \cdot 10^{-25} kgm/s$

And now we can use De Broglie's relationship to find its wavelength:
$\lambda= \frac{h}{p}= \frac{6.6 \cdot 10^{-34} Js}{9.35 \cdot 10^{-25} kg m/s} =7.06 \cdot 10^{-10}m$
where h is the Planck constant.

(b) By using the same procedure of part (a), we can convert the photon energy into Joules:
$E=3.00 eV \cdot 1.6 \cdot 10^{-19} eV/J =4.8 \cdot 10^{-19}J$

The energy of a photon is related to its frequency f by:
$E=hf$
where h is the Planck constant. Re-arranging the equation, we find
$f= \frac{E}{h}= \frac{4.8 \cdot 10^{-19} J}{6.6 \cdot 10^{-34}Js} =7.27 \cdot 10^{14}Hz$

And now we can use the relationship between frequency f, speed of light c and wavelength $\lambda$ of a photon, to find its wavelength:
$\lambda= \frac{c}{f}= \frac{3 \cdot 10^8 m/s}{7.27 \cdot 10^{14} Hz} =4.13 \cdot 10^{-7} m$

8 0

3 years ago

Which of the following is the best example of kinetic energy being transformed into potential energy

poizon [28]

A pendulum is probably the most common showing of this example. As the pendulum swings down, it converts its potential energy (height) into kinetic energy (velocity). At the lowest point the kinetic energy is the highest and the potential is the lowest. At the highest point in its swing the velocity is zero so the kinetic energy is zero and the potential energy is at a maximum (greatest height).

3 0

3 years ago

Read 2 more answers

I need these for test corrections that are due tomorrow please :)

Ivahew [28]

That would be position Y, as the northern hemisphere is tilted away from the sun.

6 0

2 years ago

There isnt enough sanitidzer(alcohol)what solution to be replaced

Alex Ar [27]

For me: WASH OUR HANDS REGULARLY

3 0

1 year ago