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3 years ago

Which protects a cell and forms it’s boundary

Physics

1 answer:

ivann1987 [24]3 years ago

5 0

Answer:

For a plant cell: The cell wall and the cell membrane

For animal cells: Just the cell membrane

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Assuming 95.0% efficiency for the conversion of electrical power by the motor, what current must the 12.0-V batteries of a 708-k

Varvara68 [4.7K]

Answer:

a) $I=646.9298\ A$

b) $I=1942.018\ A$

Explanation:

Given:

efficiency of the motor, $\eta=0.95$

voltage of the battery, $V=12\ V$

mass of the car, $m=708\ kg$

initial velocity, $u=0\ m.s^{-1}$

final velocity, $v=25\ m.s^{-1}$

time taken for the acceleration, $t=1\ min=60\ s$

Now we know by the Newton's second law of motion:

$F=m.a$

$F=708\times \frac{(25-0)}{60}$

$F=295\ N$

Now the power will be :

$P=F.v$

$P=295\times 25$

$P=7375\ W$

According to the question:

0.95 times of the electrical power should yield this mechanical power.

$P=V.I\times 0.95$

$7375=12\times I\times 0.95$

$I=\frac{7375}{12\times 0.95}$

$I=646.9298\ A$

height climbed by the car, $h=200\ m$

velocity of climb, $v=25\ m.s^{-1}$

time taken to climb the height, $t=2\ min=120\ s$

force exerted to overcome air and frictional resistances, $f=423\ N$

Now the Power required to climb the hill:

$P=\frac{m.g.h}{t} +f\times v$

$P=\frac{708\times 9.8\times 200}{120}+423\times 25$

$P=22139\ W$

Now according to the electrical efficiency:

$P=V.I\times 0.95$

$22139=12\times I\times 0.95$

$I=1942.018\ A$

7 0

4 years ago

Read 2 more answers

An Arrow (0.5 kg) travels with velocity 20 m/s to the right when it pierces an apple (2 kg) which is initially at rest. After th

sattari [20]

Answer:

4 m/s

Explanation:

From the law of conservation of momentum,

Total momentum before collision = Total momentum after collision

mu+m'u' = V(m+m')...................... Equation 1

Where m = mass of the arrow, u = initial velocity of the arrow, m' = mass of the apple, u' = initial velocity of the apple, V = Final velocity of the apple and the arrow after collision.

make V the subject of the equation

V = (mu+m'u')/(m+m').................... Equation 2

Given: m = 0.5 kg, m' = 2 kg, u = 20 m/s, u' = 0 m/s(initially at rest)

Substitute into equation 2

V = (0.5×20+2×0)/(2+0.5)

V = 10/2.5

V = 4 m/s.

Hence the final velocity of the apple and the arrow after the collision = 4 m/s

6 0

4 years ago

I need help ! if class is not finished in 10 days i’ll have to do summer school ! pls helpppp !!!!!

lara31 [8.8K]

the awnser is a and i hope that helps

5 0

3 years ago

Which of these would be a good model to demonstrate the fact that the galaxies are moving apart as the universe is expanding?

Sergio [31]

Answer: Option A: The spots on the balloon move away as the balloon is inflated.

one of the scientific models describes the galaxies are moving apart as the universe is expanding. This expansion theory came from the observation of red-shifted spectrum from all the directions indicating that the galaxies are moving away. This can be understood from the inflated balloon. Initially spots can be marked using a colored pen on the balloon.On inflating the balloon, it would be noticed that the spots on the balloon move away. Actually the position of the spots won't change, but the distance between the spots would expand. This is a good model to explain the expanding universe. The galaxies are neither moving in any random direction nor moving forward. So, rest of the options are not good models to explain the theory.

3 0

3 years ago

PLEASE HELP ME ASAP!!!!

Angelina_Jolie [31]

Two objects in physical contact with each other are in thermal equilibrium when they reach the same temperature and an exchange of heat energy no longer occurs. According to HyperPhysics, the relation of thermal equilibrium follows the Zeroth Law of Thermodynamics, which states that “if two systems are at the same time in thermal equilibrium with a third system, they are in thermal equilibrium with each other.”

6 0

4 years ago