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2 years ago

9

Which of these phase changes requires energy?

1 answer:

frutty [35]2 years ago

7 0

Answer:

A

Explanation:

You have to give energy away for B. You have to think about that carefully. The CO2 starts out with a great deal of energy (mostly KE) and has to slow down to go from gas to a solid. Not B

In general C is the same way. Water has more energy than ice. Not C

Same principle in D. Not D.

So it's A

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Give an examplea of newtons law of acceleration

coldgirl [10]

The 2nd Law of Motion states acceleration is produced when a n unbalanced force acts on an object (mass) The more mass the object has the more net force has to be used to move it.

Examples:

If you use the same force to push a truck and push a car, the car will have more acceleration than the truck, because the car has less mass.

It's easier to push a empty shopping cart then a full one, because the full one has more mass than the empty one. This means more force is required to push the full shopping cart.

8 0

3 years ago

A ball is hit 1 meter above the ground with an initial speed of 40 m/s. If the ball is hit at an angle of 30 above the horizonta

Vika [28.1K]

Answer:

$t_t=4.131\ s$

Explanation:

Given:

height above the horizontal form where the ball is hit, $y=1\ m$

angle of projectile above the horizontal, $\theta=30^{\circ}$

initial speed of the projectile, $u=40\ m.s^{-1}$

<u>Firstly we find the </u><u>vertical component of the initial velocity</u><u>:</u>

$u_y=u.\sin\theta$

$u_y=40\times \sin30^{\circ}$

$u_y=20\ m.s^{-1}$

During the course of ascend in height of the ball when it reaches the maximum height then its vertical component of the velocity becomes zero.

So final vertical velocity during the course of ascend:

$v_y=0\ m.s^{-1}$

Using eq. of motion:

$v_y^2=u_y^2-2g.h$ (-ve sign means that the direction of velocity is opposite to the direction of acceleration)

$0^2=20^2-2\times 9.8\times h$

$h=20.4082\ m$ (from the height where it is thrown)

<u>Now we find the time taken to ascend to this height:</u>

$v_y=u_y-g.t$

$0=20-9.8t$

$t=2.041\ s$

<u>Time taken to descent the total height:</u>

we've total height, $h'=h+y$ $=20.4082+1$

$h'=u_y'.t'+\frac{1}{2} g.t'^2$

during the course of descend its initial vertical velocity is zero because it is at the top height, so $u_y'=0\ m.s^{-1}$

$21.4082=0+4.9t'^2$

$t'=2.09\ s$

<u>Now the total time taken by the ball to hit the ground:</u>

$t_t=t'+t$

$t_t=2.09+2.041$

$t_t=4.131\ s$

3 0

3 years ago

A tortoise and a hare are having a 1,000-meter race. The tortolse runs the

lukranit [14]

Answer:2 hours

Explanation:

6 0

3 years ago

Any help is appreciated

sdas [7]

image distance,di=10 cm

object distance,do=20cm

magnification, m=di/do

=10/20

=0.5

since the image is virtual, magnification is negative.

therefore m=-0.5

8 0

3 years ago

An object has a mass of 5 kg a displacement of 5 m and time of 25 seconds what is the momentum

PSYCHO15rus [73]

Answer:

1 Ns

Explanation:

Velocity = Displacement / time taken

v = 5/25 ⇒ v = 0.2 ms⁻¹

Momentum = mass × velocity

= 5 × 0.2 = 1 Ns

6 0

3 years ago