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1 year ago

1. Sang Hee rubs a balloon on her hair until, when she holds the balloon several inches from

Physics

1 answer:

vodomira [7]1 year ago

7 0

The reason why Kim's hair rises and sticks out is due to electrostatic attraction.

<h3>What is charging by friction?</h3>

We know that one of the ways in which a body is able to acquire static charges is by friction. When a body is rubbed against another, there could be loss or gain of charges leaving a net charge on each body.

The process that occurs when some of Kim's hair rises and sticks out toward the balloon, even though the balloon hasn't touched her hair is electrostatic attraction.

Learn more about charging by friction:brainly.com/question/9201910

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What is the efficiency of the machine if the input is 263 J and the output is 142 J?

Papessa [141]

Answer: 57.79%

Explanation: 152J/263J=.577946768 or 57.79% or roundedthe nearest whole percent is 58%

7 0

3 years ago

Damping is negligible for a 0.135-kg object hanging from a light, 6.30-N/m spring. A sinusoidal force with an amplitude of 1.70

IceJOKER [234]

Answer:

0.72 Hz minimum frequency

Explanation:

When the damping is negligible,Amplitude is given as

$A = (F/m)/[\sqrt{(\omega ^{^{2}}-\omega _{o}^{2}})^2$

here $\omega _{o}^{2}= k/m$ = (6.30)/(0.135) = 46.67 N/m kg

$F / mA$ = 1.70/(0.135)(0.480) = 26.2 N/m kg

From the above equation , rearranging for ω,

$\omega ^{2}= \omega _{o}^{2}\pm F/m$

⇒ ω² =46.67 ± 26.2 = 72.87 or 20.47

⇒ ω = 8.53 or 4.52 rad/s

Frequency = f

ω=2 π f

⇒ f = ω / 2π = 8.53 /6.28 or 4.52 / 6.28 = 1.36 Hz or 0.72 Hz

The lower frequency is 0.72 Hz and higher is 1.36 Hz

8 0

3 years ago

Radio waves travel at 3.00 · 108 m/s. Calculate the wavelength of a radio wave of frequency 900 kHz. (9.00 · 105 Hz.)

Anuta_ua [19.1K]

V: velocity of wave
f: frequency
L: wavelenght

v = fL => L = v/f => L = (3x10^8)/(900x10^3) => L = 3.33 x 10^2m

7 0

3 years ago

A skater has rotational inertia 4.2 kg.m2 with his fists held to his chest and 5.7 kg.m2 with his arms outstretched. The skater

Fynjy0 [20]

Answer:

6.13428 rev/s

Explanation:

$I_f$ = Final moment of inertia = 4.2 kgm²

I = Moment of inertia with fists close to chest = 5.7 kgm²

$\omega_i$ = Initial angular speed = 3 rev/s

$\omega_f$ = Final angular speed

r = Radius = 76 cm

m = Mass = 2.5 kg

Moment of inertia of the skater is given by

$I_i=I+2mr^2$

In this system the angular momentum is conserved

$L_f=L_i\\\Rightarrow I_f\omega_f=I_i\omega_i\\\Rightarrow \omega_f=\dfrac{I_i\omega_i}{I_f}\\\Rightarrow \omega_f=\dfrac{(5.7+2\times 2.5\times 0.76^2)3}{4.2}\\\Rightarrow \omega_f=6.13428\ rev/s$

The rotational speed will be 6.13428 rev/s

5 0

3 years ago

The gun, mount, and train car of a railway had a total mass of 1.22 x 10^6 kg. The gun fired a projectile that was 80 cm in diam

kakasveta [241]

1) According to the law of conservation of momentum ..
Horiz recoil mom of gun (M x v) = horiz. mon acquired by shell (m x Vh) 

1.22^6kg x 5.0 m/s = 7502kg x Vh 
Vh = 1.22^6 x 5 / 7502 .. .. Vh = 813 m/s 

Barrel velocity V .. .. cos20 = Vh / V .. ..V = 813 /cos20 .. .. ►V = 865 m/s 

2) Using the standard range equation .. R = u² sin2θ /g 

R = 865² x sin40 / 9.80 .. .. ►R = 49077 m .. (49 km)

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3 years ago