A basketball is resting on the ground.

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

3 years ago

The noise level coming from a pig pen with

sweet [91]

Answer:

The decibel of the remaining pigs is 51.5 dB.

Explanation:

Decibel (dB) is a unit of measure of the intensity of a given sound.

Number of pigs = 199, noise level = 74.3 dB.

Given that the intensity (I) of the sound from the pen is proportional to the number of pigs (N), thus:

I $\alpha$ N

I = kN

where k is the constant of proportionality.

⇒ k = $\frac{I}{N}$

= $\frac{74.3}{199}$

k = 0.3734

When 61 numbers of pigs were removed, the number of remaining pigs (N) squealing at their original level is 138.

Thus, the becibel level (I) of the remaining pigs can be determined by:

I = kN

= 0.3734 × 138

= 51.53 dB

The becibel level (I) of the remaining pigs is 51.53 dB.

6 0

3 years ago

Which describes why people on earth can see light from the stars in the sky that are so far away?

Ugo [173]

Yes, C is correct. It self explains itself as we know light travels through a vacuum ( doesn't need a medium) and light is a type of electromagnetic wave.

7 0

3 years ago

a person was using a spanner to loosen a tight nut.Their mass was 50kg the spanner was 0.5m long i) what is the persons weight?

sineoko [7]

1) Weight of the person: 490 N

2) Maximum torque: 245 Nm

Explanation:

1)

The weight of a body is equal to the gravitational force exerted on the body; it is given by the equation

$F=mg$

where

m is the mass of the body

g is the acceleration due to gravity

For the person in this problem,

m = 50 kg is the mass

$g=9.8 m/s^2$ is the acceleration due to gravity on Earth's surface

Therefore, the weight of the person is

$F=(50)(9.8)=490 N$

2)

The turning force (also called torque) exerted by a force rotating an object is given by

$\tau = Fd sin \theta$

where

F is the magnitude of the force

d is the length of the arm (the distance between the force and the pivotal point)

$\theta$ is the angle between the direction of the force and the arm

For the spanner in this problem,

F = 490 N is the force applied (the weight of the person)

d = 0.5 m is the arm (the length of the spanner)

The maximum torque is obtained when $\theta=90^{\circ}$ , therefore it is:

$\tau=(490)(0.5)(sin 90^{\circ})=245 N\cdot m$

Learn more about weight:

brainly.com/question/8459017

brainly.com/question/11292757

brainly.com/question/12978926

About torque:

brainly.com/question/5352966

#LearnwithBrainly

5 0

3 years ago

Two spaceships that have different masses but rocket engines of identical force are at rest in space. if they fire their rockets

NISA [10]

Force is calculated F=m×a.
If both ships speed up with the same force, but have a different mass, This means that a also has to be different. If F is the same but ship a has a bigger mass(m) than ship b, then the acceleration(a) of ship b has to be bigger so F of each ship is the same. So the ship with the smaller mass will speed up faster.

5 0

3 years ago