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andrew-mc [135]
3 years ago
15

When pushing a child on a swing, you must give them a push periodically to keep them moving. This seems to go against the law of

inertia and the conservation of energy.
When pushing a child on a swing, you must give them a push periodically to keep them moving. This seems to go against the law of inertia and the conservation of energy. Why does the child need a push periodically to keep moving.

A) Energy is lost over time slowing down the swing.
B) All objects will naturally come to rest over time.
C) A wind must have been blowing in the opposite direction.
D) Friction provides an outside force slowing the swing down.
Physics
2 answers:
Alekssandra [29.7K]3 years ago
4 0

Answer: D) Friction provides an outside force slowing the swing down.

Explanation: Inertia states that an outside force is needed to change the motion of an object. Friction provides an outside force slowing the swing down.

nikdorinn [45]3 years ago
3 0

Answer:DFriction provides an outside force slowing the swing down.

Explanation:

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The work function of a metal surface is 4.80 × 10-19 J. The maximum speed of the electrons emitted from the surface is vA = 7.7
poizon [28]

Answer:

\lambda_A=2.65177\times 10^{-7}\ m

\lambda_B=3.32344\times 10^{-7}\ m

Explanation:

h = Planck's constant = 6.63\times 10^{-34}\ m^2kg/s

c = Speed of light = 3\times 10^8\ m/s

m = Mass of electron = 9.11\times 10^{-31}\ kg

W_0 = Work function = 4.8\times 10^{-19}\ J

v_A = Velocity of A particle = 7.7\times 10^5\ m/s

v_B = Velocity of B particle = 5.1\times 10^5\ m/s

The wavelength is given by

\lambda=\frac{hc}{\frac{1}{2}mv^2+W_0}

\lambda_A=\frac{6.63\times 10^{-34}\times 3\times 10^8}{\frac{1}{2}9.11\times 10^{-31}(7.7\times 10^5)^2+4.8\times 10^{-19}}\\\Rightarrow \lambda_A=2.65177\times 10^{-7}\ m

The wavelength \lambda_A=2.65177\times 10^{-7}\ m

\lambda_B=\frac{6.63\times 10^{-34}\times 3\times 10^8}{\frac{1}{2}9.11\times 10^{-31}(5.1\times 10^5)^2+4.8\times 10^{-19}}\\\Rightarrow \lambda_B=3.32344\times 10^{-7}\ m

The wavelength \lambda_B=3.32344\times 10^{-7}\ m

5 0
4 years ago
What is the time required for sound to travel 1.75 km if the temp of the air is 20 C°?
murzikaleks [220]

Answer:

Explanation:

The 2 equations we need for this are

v=331.5+.606T and

d = rt. First we need to find the velocity using the first equation, then we will plug it into the distance equation as the rate to find the time.

v = 331.5 + .606(20.0) I used 3 sig figs for the temp instead of the 1 found in 20.

v = 331.5 + 12.1 so

v = 343.6 m/s

Now, before we can find the time in seconds, we need to convert the distance to meters.

1.75 km = 1750 m:

1750 = 343.6t so

t = 5.09 seconds

7 0
3 years ago
A gamma ray photon has an energy of 0.91 GeV. (1 GeV = 109 eV.) What is the wavelength of the gamma ray in fm? (1 fm = 10-15 m)?
anastassius [24]

Answer:

\lambda=1.37 fm

Explanation:

The Planck Eistein relation, states that the energy of a photon is proportional to its frequency:

E=h\nu(1)

h is the Plank constant.The frequency of a photon is defined as the speed of light over its wavelength:

\nu=\frac{c}{\lambda}(2)

Replacing (2) in (1):

E=\frac{hc}{\lambda}\\\lambda=\frac{hc}{E}\\\lambda=\frac{(4.14*10^{-15}eV\cdot s)(3*10^8\frac{m}{s})}{0.91*10^{9}eV}\\\\\lambda=(1.37*10^{-15}m)*\frac{1fm}{10^{-15}m}\\\\\lambda=1.37 fm

6 0
3 years ago
What is true about an object in free fall?
salantis [7]
The only force being acted upon it is gravity. A ball that was thrown downward off a building isn't in freefall, because it had initial velocity. A piece of paper can't necessarily be in free fall because it is affected by air resistance.
5 0
3 years ago
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