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4 years ago

7

The human body is an organism made up of cells, tissues, organs, and organ system. Here are examples of three types of muscle ti

ssue that are made of very different cells. How can scientists determine what type of cells make up each of these three tissues? A) By using a magnifying glass to observe each tissue. B) By collecting the tissues of people who have died and making observations. C) By dissecting the tissues and then making observations using a dissecting scope. Eliminate D) By placing samples of each tissue on a slide and viewing the slides using a microscope.

1 answer:

REY [17]4 years ago

8 0

I would think that would be C.

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a 45kg boy is holding a 12kg pumpkin while standing on ice skates on a smooth frozen pond. the boy tosses the pumpkin with a hor

irga5000 [103]

Let's split the problem into two parts, and let's solve it by using conservation of momentum.

1) Let's analyze the moment when the boy tosses the pumpkin. Before this moment, the boy is standing with the pumpkin, so with speed v=0 and therefore the total momentum of the system (boy+pumpkin) is zero.
After he tosses the pumpkin, the boy will start to move with speed $v_b$ and the pumpkin starts to move with speed $v_p=2.8 m/s$ . The momentum of the boy is $m_b v_b$ (with $m_b =45 kg$ being the mass of the boy), while the momentum of the pumpkin is $m_p v_p$ (where $m_p=12 kg$ is the mass of the pumpkin). Since the total momentum must be equal to zero (because the total momentum cannot change), then we can write
$m_b v_b + m_p v_p =0$
From which we find
$v_b = - \frac{m_p v_p}{m_b}=- \frac{(12 kg)(2.8 m/s)}{45 kg} =-0.75 m/s$
and this is the speed of the boy, and the negative sign means he's moving in the opposite direction of the pumpkin.

2) Now let's focus on the entire system (boy+pumpkin+girl). Initially, the total momentum of this system is zero, because both the boy (holding the pumpkin) and the girl are still. So, the total momentum after the girl catches the pumpkin must be still zero.
After this moment, the boy has a momentum of $m_b v_b$ , while the girl has momentum $(m_g+m_p)v_g$ where $m_g=37 kg$ is the girl mass $v_g$ is the girl speed. Here we use $m_g+m_p$ because the girl is holding the pumpkin now. Therefore, the conservation of momentum becomes
$m_bv_b + (m_g+m_p)v_g =0$
and so
$v_g = - \frac{m_b v_b}{m_g+m_p} =- \frac{(45 kg)(-0.75 m/s)}{37 kg+12 kg} =0.69 m/s$
and this is the girl's speed, with positive sign so with same direction of the pumpkin initial direction.

6 0

4 years ago

If you cook a marshmallow a few feet above a camp fire, it will cook mostly

nasty-shy [4]

Answer:

A) radiation.

Explanation:

Hello,

In this case, heat transfer from a body with a high temperature to a body with a lower temperature may occur when the bodies are not in direct physical contact with each other or when they are separated in space and it is is called heat radiation. Solids, liquids, or gaseous substances are able to emit energy via a process of electromagnetic radiation because of vibrational and rotational movement of their molecules and atoms.

Hence, since the camp fire is not in contact with the marshmallow and it still cooks it, we can infer that the mechanism of heat transfer is A) radiation. Moreover, both conduction and convection occur when the bodies are in contact.

Regards.

6 0

3 years ago

A wave of amplitude 20mm has intensity Ix. Another wave of the same frequency but of amplitude 5mm has an intensity Iy.

Alexeev081 [22]

Answer:

(C) 16

Explanation:

Given:

The amplitude of first wave (s₁) = 20 mm

The amplitude of second wave (s₂) = 5 mm

Intensity of first wave = Iₓ

Intensity of second wave = $I_y$

The intensity associated with a wave depends on the amplitude of the wave.

The intensity (I) is directly proportional to the square of the amplitude (s) of the wave and is expressed as:

$I=ks^2\\Where\ k\to constant\ of\ proportionality$

Now, the intensities of the two waves are given as:

$I_x=ks_1^2=k(20)^2\\\\I_y=ks_2^2=k(5)^2$

Dividing both the intensities, we get:

$\frac{I_x}{I_y}=\frac{k(20)^2}{k(5)^2}\\\\\frac{I_x}{I_y}=\frac{400}{25}\\\\\frac{I_x}{I_y}=16$

Therefore, the option (C) is correct.

5 0

3 years ago

What can be known about electrons?

BlackZzzverrR [31]

Electrons carry a negative charge.

8 0

3 years ago

A car is stopped at a red light. When the light turns green, the car accelerates until it reaches a final velocity of 45 m/s. It

tigry1 [53]

Answer:

270 m

Explanation:

We can find the distance travelled by the car by using the following suvat equation:

$s=(\frac{u+v}{2})t$

where

s is the distance travelled

u is the initial velocity

v is the final velocity

t is the time

For the car in this problem,

u = 0

v = 45 m/s

t = 12 s

Substituting into the equation, we find:

$s=(\frac{0+45}{2})(12)=270 m$

8 0

3 years ago