What is the density of 15 cm3 and 3 g?

How do scientists know our universe is older than 6500 years?

dmitriy555 [2]

<span>This is because astronomers have discovered that the Crab Nebula is 6500 light years from earth. This means it takes 6500 earth years for light to get from the Crab Nebula to earth. Therefore, if we are able to observe the Crab Nebula and beyond it then it means that earth has been in existence for 6500 years and over. </span>

5 0

3 years ago

A 40 kg skateboarder runs at a constant velocity of 12 m/s and jumps off a stationary skateboard with a mass of 8 kg. What is th

horsena [70]

Answer:

60 m/s (in the opposite direction)

Explanation:

By conservation of momentum,

Initial momentum of board + Initial momentum of man = Final momentum of board + Final momentum of man

=> 0 + 40*12 = 8*(-v) + 0

=> v = -60 [ Negative indicates opposite direction ]

7 0

4 years ago

An object executing simple harmonic motion has a maximum speed of 4.3 m/s and a maximum acceleration of 0.65 m/s2 . find (a) the

Alexxx [7]

(1) The position around equilibrium of an object in simple harmonic motion is described by
$x(t) = A \cos (\omega t)$
where
A is the amplitude of the motion
$\omega$ is the angular frequency.

The velocity is the derivative of the position:
$v(t)=-\omega A \sin(\omega t) = -v_0 \sin (\omega t)$
where
$v_0 = \omega A$ is the maximum velocity of the object.

The acceleration is the derivative of the velocity:
$a(t)=- \omega^2 A \cos (\omega t) = -a_0 \cos (\omega t)$
where
$a_0=\omega^2 A$ is the maximum acceleration of the object.

We know from the problem both maximum velocity and maximum acceleration:
$v_0 = \omega A = 4.3 m/s$
$a_0 = \omega^2 A = 0.65 m/s^2$
From the first equation, we get
$A= \frac{4.3 }{\omega}$ (1)
and if we substitute this into the second equation, we find the angular fequency
$\omega=0.15 rad/s$
while the amplitude is (using (1)):
$A=28.7 m$

(b) We found in the previous step that the angular frequency of the motion is
$\omega=0.15 rad/s$
But the angular frequency is related to the period by
$T= \frac{2 \pi}{\omega}$
and so, the period is
$T= \frac{2 \pi}{\omega}= \frac{2 \pi}{0.15 rad/s}=41.9 s$

5 0

3 years ago

Select the correct answer. What does the law of conservation of energy state? A. Energy can be created from nothing. B. Energy c

Anarel [89]

Answer: c

Explanation:

4 0

3 years ago

Read 2 more answers

A projectile is fored vertically upward with an initial velocity of 190 m/s. Find the maximum height of the projectile.

RSB [31]

Answer:

3683.67 m

Explanation:

Formula for maximum height of projectile is given by the equation;

h = u²/2g

Where u is initial velocity and g is acceleration due to gravity

We are given u = 190 m/s

Thus;

h = 190²/9.8

h = 36100/9.8

h = 3683.67 m

6 0

3 years ago