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4 years ago

Why doesn’t the ball roll on forever after being kicked at a soccer game?

1 answer:

7 0

My guess would be because the gravity from the Earth's core is constantly pulling the ball towards the ground. It's like the moon. Why doesn't the moon just float away in space? Because Earth's gravitational pull keeps it rotating around it. Therefore, the ball will always be pulled towards the core which keeps it from from rolling forever due to friction. But i may be wrong, even though this a quite a good answer, hope it is right!

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The hot glowing surfaces of stars emit energy in the form of electromagnetic radiation. it is a good approximation to assume tha

Rufina [12.5K]

This assumption is correct. The emissivity of a substance is the ratio of the energy radiated from a body to the energy radiated from a black body (perfect emitter). Because these stars reflect negligible radiation compared to the amount they emit.

6 0

3 years ago

The aluminum wire in a high-voltage transmission line is 2.7 cm in diameter. It is designed to carry a current of 1100 A. What i

marissa [1.9K]

Answer:

1660 V

Explanation:

Resistance should be determined and then voltage drop across the power line can be determined.

R = ρ L /A

Here ρ = Resistivity of aluminum = $2.7\times 10^{-8}\Omega m$

L = length = 32 km = 32,000 m

Area of cross section = A = π r² = π (0.027/2)² = 0.00057255 m²

Resistance = R =

( $2.7\times 10^{-8}\Omega m$ (32,000)/(0.00057255) = 1.5090 Ohms.

Voltage drop = V = I R = (1100)(1.5090) = 1659.9 V.

(If resistivity value is different, then the resistance will be different and hence final answer for voltage will also vary ).

4 0

3 years ago

A student used a tuning fork of frequency 320 Hz and observed that the speed of sound was 339 m/s. Calculate the wavelength of t

Helen [10]

To solve this problem it is necessary to apply the concepts related to wavelength as a function of speed and frequency. In mathematical terms it can be expressed as

$\lambda = \frac{v}{f}$

Where,

v = Velocity

f = Frequency

According to our values the frequency (f) is 320Hz and the speed (v) is 339m / s.

Replacing in the given equation we have to,

$\lambda = \frac{v}{f}\\\lambda = \frac{339}{320}\\\lambda = 1.059m\approx 1.06m$

Therefore the wavelength of this sound wave is 1.06m

5 0

3 years ago

An electric current heats a 221 g (0.221 kg) copper wire from 20.0 Â°C to 38.0 Â°C. How much heat was generated by the current?

lorasvet [3.4K]

Answer:

Heat generated by the current = 1547.89 J

Explanation:

We have equation for heat energy H = mCΔT

Mass of copper = 0.221 kg

Specific heat of copper = 0.093 kcal/kgC° = 389.112 J/kgC°

ΔT = 38 - 20 = 18°C

Substituting in H = mCΔT

H = 0.221 x 389.112 x 18 = 1547.89 J

Heat generated by the current = 1547.89 J

3 0

4 years ago

Describe briefly the potential energy it has ( roller coaster)

jek_recluse [69]

Answer:

The energy that it starts with at the top of the inclinede Plane

Explanation:

Hope I helped:)

5 0

3 years ago