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1 year ago

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The law of reflection states that the angle of incidence and the angle of reflection will ______.Select one:a.never be equalb. a

lways add up to 90 degreesc.always add up to 180 degreesd.always be equal

1 answer:

Dmitry [639]1 year ago

4 0

The law of reflection states that the angle of incidence and the angle of reflection will always be equal.

When a ray of light reflects off a surface, the angle of reflection is equal to the angle of incidence.

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The Carson family's pancake recipe uses 2 teaspoons of baking powder for every 1/3 of a teaspoon of salt. How much baking powder

melomori [17]

Answer:

6 teaspoons of baking powder required.

Explanation:

Given that

According to the recipe of pancake,

For every $\frac{1}{3}$ teaspoon of salt, 2 teaspoons of baking baking powder is required.

To find:

How much baking powder will be needed, if 1 teaspoon of salt was used ?

Solution:

This problem can be solved using ratio.

$\frac{1}3$ teaspoon of salt : 2 teaspoons of baking powder

Let us multiply the above ratio with 3.

$\frac{1}{3}\times 3$ teaspoon of salt : 2 $\times$ 3 teaspoons of baking powder

OR

1 teaspoon of salt : 6 teaspoons of baking powder

So, answer is <em>6 teaspoons </em>of baking powder required.

Also, we can use the unitary method:

$\frac{1}3$ teaspoon of salt needs = 2 teaspoons of baking powder

1 teaspoon of salt needs = $\frac{2}{\frac{1}3}$ teaspoons of baking powder

1 teaspoon of salt needs = 2 $\times$ 3 = <em>6</em> teaspoons of baking powder needed

So, the answer is:

<em>6 teaspoons of baking powder </em>required.

5 0

3 years ago

Read 2 more answers

Two people stand facing each other at roller skating rink then push off each other

9966 [12]

a) 0 kg m/s

b) 0 kg m/s

c) +3 m/s

d) 60 N

Explanation:

a)

The momentum of an object is a vector quantity given by:

$p=mv$

where

m is the mass of the object

v is the velocity of the object

In this problem, we have a system of two people, so the total momentum will be the sum of the individual momenta of the two people:

$p=p_1 + p_2$

Which can be rewritten as

$p=m_1 u_1 + m_2 u_2$

where $m_1,m_2$ are the masses of the two people and $u_1,u_2$ their initial velocities.

However, the two people are initially at rest, so

$u_1 = 0\\u_2 = 0$

Therefore the total momentum is

$p=0+0=0$

b)

The principle of conservation of momentum states that when there are no external forces acting on a system, the total momentum of the system is conserved, so we can write:

$p_i = p_f$

where

$p_i$ is the total momentum of the system before

$p_f$ is the total momentum of the system after

In this problem,

$p_i = 0$

As we calculated in part a: this is because the total momentum of the two people before they push off each other is zero.

Therefore, according to the law of conservation of momentum,

$p_f = p_i = 0$

So the total momentum is zero also after they push off each other.

c)

The total momentum of the girl and the boy after they push off each other can be written as:

$p_f = m_1 v_1 + m_2 v_2$ (1)

where:

$m_1 = 30 kg$ is the mass of the girl

$v_1 = -5 m/s$ is her velocity (she moves backward, so the negative sign)

$m_2 = 50 kg$ is the mass of the boy

$v_2$ is the velocity of the boy

As calculated in part b), we also know that the total momentum of the girl and the boy is

$p_f = 0$ (2)

By combining eq(1) and eq(2) we get

$0=m_1 v_1 + m_2 v_2$

And solving for v2 we find the velocity of the boy:

$v_2=-\frac{m_1 v_1}{m_2}=-\frac{(30)(-5)}{50}=+3 m/s$

and the positive sign means he is moving forward.

d)

We can solve this part by applying the impulse theorem, which states that the change in momentum of an object is equal to the product between the force applied on it and the duration of the collision:

$\Delta p = F\Delta t$

where

$\Delta p$ is the change in momentum

F is the force

$\Delta t$ is the time during which the force is applied

In this problem:

$\Delta t = 2.5 s$

For the boy, the change in momentum is:

$\Delta p = m_2 (v_2 - u_2)$

And since

$m_2 = 50 kg\\u_2 = 0 m/s\\v_2 = 3 m/s$

We have

$\Delta p = (50)(3-0)=150 kg m/s$

So, the force exerted between the boy and the girl is:

$F=\frac{\Delta p}{\Delta t}=\frac{150}{2.5}=60 N$

8 0

3 years ago

Why are chemical changes considered “unseen”?

jeka57 [31]

<span>Because they occur at an atomic level, changing the actual structure of the thing.

</span>

7 0

3 years ago

Read 2 more answers

In order for work to take place the energy present must be related to the movement of the object.

kaheart [24]

This is another one of those muddy misleading questions, followed by
a muddy group of choices from which an answer must be selected.

a). is absurd. There's no such thing as a "balanced force", only
a balanced group of forces.

b). is probably the choice the question is aiming for.

c). is not so. The engines of an airplane do plenty of work lifting the plane
off the ground, although the force of the engines is never directed upward.

d). is really awkward. The object's motion is almost never the cause of the force.
The force is almost always the cause of the object's motion.

Now for the big 800-lb gorilla in the room: No moving object needs to be involved
in order for energy to be flowing or work to be getting done.

-- A radio wave radiates through space. Straighten out a wire coat-hanger and
stick it up in the air where the radio wave can pass by it. Electrical current flows
through the wire, and you can drain the electrical energy out the bottom of it.

-- A light bulb is shining. Some distance away, something it's shining on
gets warm, because of the heat energy that has shot across to it from the
light bulb and soaked into it.

-- A lightning bolt jumps from the ground to a passing cloud. Or, if you feel
more comfortable with it, a lightning bolt jumps from a cloud to the ground.
It doesn't matter. Either way, there's enough energy splashing around to
ignite houses, zap TVs and computers, melt concrete, vaporize water, and
light up a city. Although nothing is moving.

5 0

3 years ago

A 38-kg canoe breaks free from its dock and floats downriver at a speed of 2.2 m/s. What is the momentum of the canoe? 48.0 m/s

Brut [27]

Momentum of a body is calculated by multiplying the mass of a moving body with its velocity. When a body is at rest it has zero momentum since the velocity is also zero.
In this case the momentum of the canoe will be;
38 kg × 2.2 m/s = 83.6 kgm/s
Therefore, the correct answer is 83.6 kg m/s

3 0

3 years ago