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3 years ago

I’m not sure how to do 30, could someone pls help?

Physics

1 answer:

choli [55]3 years ago

8 0

I think its C or D.

Einstein's Nobel winning photoelectric equation.

The higher the work function, the more energy needed to photoeject an electron from the surfface

Try D

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The count rate of a radioactive source decreases from 1600 counts per minute to 400 counts per minute in 12 hours. What is the h

kirill115 [55]

Answer:

$t_{1/2}=6 h$

Explanation:

Let's use the decay equation.

$A=A_{0}e^{-\lambda t}$

Where:

A is the activity at t time
A₀ is the initial activity
λ is the decay constant

We know that $\lambda=\frac{ln(2)}{t_{1/2}}$

So we have:

$\lambda=\frac{ln(A/A_{0})}{t}$

$\frac{ln(2)}{t_{1/2}}=\frac{ln(A/A_{0})}{t}$

$t_{1/2}=\frac{t*ln(2)}{ln(A/A_{0})}$

$t_{1/2}=6 h$

Therefore, the half-life of the source is 6 hours.

I hope it helps you!

4 0

3 years ago

A ball is spun around in circular motion such that it completes 50 rotations in 25 s. What is the frequency of its rotation? 2.

Elis [28]

Answer:

1. $f = 2 Hz$

2. $f = 0.011 Hz$

3. $f = 0.067 Hz$

4. $t = 4 s$

Explanation:

1. The frequency of rotation is given by:

$f = \frac{\omega}{2\pi}$

Where:

ω: is the angular speed = 50 rotations (revolutions) in 25 s.

We need to convert the units of ω.

$\omega = \frac{50 rev}{25 s}*\frac{2\pi rad}{1 rev} = 4\pi rad/s$

Now, the frequency is:

$f = \frac{4\pi rad/s}{2\pi} = 2 Hz$

2. The frequency is:

We know:

5 laps = 5 revolutions

t: time = 450 s

$f = \frac{\omega}{2\pi} = \frac{\frac{5 rev}{450 s}*\frac{2\pi rad}{1 rev}}{2\pi} = 0.011 Hz$

3. The frequency of the pendulum is:

$f = \frac{\omega}{2\pi} = \frac{\frac{1 rev}{15 s}*\frac{2\pi rad}{1 rev}}{2\pi} = 0.067 Hz$

4. We have:

θ: number of revolutions = 48 rev

f = 12 Hz

t =?

The time can be calculated as follows:

$f = \frac{\omega}{2\pi} = \frac{\theta}{2\pi t}$

$t = \frac{\theta}{2\pi f} = \frac{48 rev*\frac{2\pi rad}{1 rev}}{2\pi*12 Hz} = 4 s$

I hope it helps you!

4 0

3 years ago

22. (I) A car slows down from 28 m/s to rest in a distance of

lidiya [134]

Answer:

a = -8.912 m/s²

Explanation:

Given,

The initial velocity of the car, u = 28 m/s

The final velocity of the car, v = 0

The distance traveled by car, d = 88 m

The velocity displacement relation is given by the formula

v = d/t

∴ t = d/v

Substituting in the above values in the given equation

t = 88/28

= 3.142 s

The acceleration is given by the formula

a = (v-u)/t

= (0 - 28)/3.142

= -8.912 m/s²

The negative sign is that the car is decelerating.

Hence, acceleration a = -8.912 m/s²

7 0

4 years ago

The work of brain mind interface is to

Genrish500 [490]

The work of Brian mind interface is to learn that’s my guess lol

4 0

4 years ago

What travels faster, light or sound?

Allushta [10]

Answer:

light travels faster than sound

4 0

3 years ago

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