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coldgirl [10]
3 years ago
8

6th grade science please help​

Physics
2 answers:
soldi70 [24.7K]3 years ago
7 0
Convention the last one.
katovenus [111]3 years ago
6 0
The answer is convention the last one
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A DJ starts up her phonograph player. The turntable accelerates uniformly from rest, and takes t1 = 11.9 seconds to get up to it
Degger [83]

Answer:

a)\omega_1=8.168\,rad.s^{-1}

b)n_1=7.735 \,rev

c)\alpha_1 =0.6864\,rad.s^{-2}

d)\alpha_2=4.1454\,rad.s^{-2}

e)t_2=1.061\,s

Explanation:

Given that:

  • initial speed of turntable, N_0=0\,rpm\Rightarrow \omega_0=0\,rad.s^{-1}
  • full speed of rotation, N_1=78 \,rpm\Rightarrow \omega_1=\frac{78\times 2\pi}{60}=8.168\,rad.s^{-1}
  • time taken to reach full speed from rest, t_1=11.9\,s
  • final speed after the change,  N_2=120\,rpm\Rightarrow \omega_2=\frac{120\times 2\pi}{60}=12.5664\,rad.s^{-1}
  • no. of revolutions made to reach the new final speed,  n_2=11\,rev

(a)

∵ 1 rev = 2π radians

∴ angular speed ω:

\omega=\frac{2\pi.N}{60}\, rad.s^{-1}

where N = angular speed in rpm.

putting the respective values from case 1 we've

\omega_1=\frac{2\pi\times 78}{60}\, rad.s^{-1}

\omega_1=8.168\,rad.s^{-1}

(c)

using the equation of motion:

\omega_1=\omega_0+\alpha . t_1

here α is the angular acceleration

78=0+\alpha_1\times 11.9

\alpha_1 = \frac{8.168 }{11.9}

\alpha_1 =0.6864\,rad.s^{-2}

(b)

using the equation of motion:

\omega_1\,^2=\omega_0\,^2+2.\alpha_1 .n_1

8.168^2=0^2+2\times 0.6864\times n_1

n_1=48.6003\,rad

n_1=\frac{48.6003}{2\pi}

n_1=7.735\, rev

(d)

using equation of motion:

\omega_2\,^2=\omega_1\,^2+2.\alpha_2 .n_2

12.5664^2=8.168^2+2\alpha_2\times 11

\alpha_2=4.1454\,rad.s^{-2}

(e)

using the equation of motion:

\omega_2=\omega_1+\alpha_2 . t_2

12.5664=8.168+4.1454\times t_2

t_2=1.061\,s

4 0
4 years ago
A microscope that uses light and more than one lens
gulaghasi [49]
A compound optical microscope or just a optical microscope is a microscope that uses light and has more than one lens.
4 0
3 years ago
Read 2 more answers
The instantaneous speed of a particle moving along one straight line is v(t) = ate−6t, where the speed v is measured in meters p
beks73 [17]

Answer:

v_max = (1/6)e^-1 a

Explanation:

You have the following equation for the instantaneous speed of a particle:

v(t)=ate^{-6t}   (1)

To find the expression for the maximum speed in terms of the acceleration "a", you first derivative v(t) respect to time t:

\frac{dv(t)}{dt}=\frac{d}{dt}[ate^{-6t}]=a[(1)e^{-6t}+t(e^{-6t}(-6))]  (2)

where you have use the derivative of a product.

Next, you equal the expression (2) to zero in order to calculate t:

a[(1)e^{-6t}-6te^{-6t}]=0\\\\1-6t=0\\\\t=\frac{1}{6}

For t = 1/6 you obtain the maximum speed.

Then, you replace that value of t in the expression (1):

v_{max}=a(\frac{1}{6})e^{-6(\frac{1}{6})}=\frac{e^{-1}}{6}a

hence, the maximum speed is v_max = ((1/6)e^-1)a

5 0
3 years ago
What is energy? Where does it come from? What does it do? Explain in 5 or more sentences please! :)
Vlada [557]

Answer:

Energy is defined as the ability to do work. Forms of energy could be kinetic energy or potential energy. Thermal or heat energy can originate from a hot object such as the sun. Energy is used to produce work. Electrical energy for lighting purposes and heating in homes and factories.

Explanation:

Energy is defined as the ability to do work and can be in various forms such as kinetic energy, potential energy, thermal, chemical, electrical energy etc.

Energy origination depends on the type of energy form in discussion. Thermal or heat energy can originate from a hot object such as the sun or an iron box, chemical energy originates from the interaction of atoms and molecules and electrical energy can be initiated by movements of electrons.

Energy is used to produce work. Different forms of energy can do different tasks such as;

Heat energy for heating water

Electrical energy for lighting purposes

Geothermal energy for producing heat and electricity

Nuclear energy for production of nuclear power

Chemical energy for facilitating chemical reactions

4 0
3 years ago
If a football player does 39000 J of work, how much power does the football player exert in 5 minutes
Drupady [299]

Answer:

Power = 130 watt

Explanation:

Power is described as the ability to do work, it is also defined as the amount of work in Joules done in a given time in seconds. Mathematically, it is represented as:

power = \frac{work (J)}{Time (s)}

In this example, power is calculated as follows:

Work = 39000 J

Time = 5 minutes

converting the time from minutes to seconds:

1 minute = 60 seconds

∴ 5 minutes = 60 × 5 = 300 seconds

\therefore power = \frac{39000}{300} \\power = 130 watt

N:B the unit for power can also be represented as Joules/seconds or J/s or JS⁻¹

6 0
3 years ago
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