Exercise Book: 18
A piece of
radioactive material contains
2000 atoms. If its half life is 20 seconds
the time take for 125 atoms to remain is?

Answer:

D. No, the cannonball will fall short of the goal

Explanation:

Based on the information given in the problem,  No, the cannonball will fall short of the goal, therefore the correct answer is option D.

There are three equations of motion given by Newton,

v = u + at

S = ut + 1/2×a×t²

v² - u² = 2×a×s

As given in the problem a  cannonball is launched off a 100 m cliff horizontally with an initial velocity of 50 m/s. The goal is to have the cannonball travel a target distance of 400 meters,

By using the second equation of motion in the vertical direction,

100 = ut + 0.5*9.81*t²

t = 4.51 seconds

The distance traveled by the cannonball in the horizontal direction at the same time = 4.51*50

                 =205 meters

Thus, based on the information given in the problem,  No, the cannonball will fall short of the goal, therefore the correct answer is option D.

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Explanation:

Force is push or pull on a body.

Contact force is a force that requires contact. It acts between two body that touches on another.

Examples are pushing a car, ringing a bell, kicking a ball.

Non contact forces are forces applied to another object without contact. The action of this force is usually through a targeted force field.

Examples are magnetic force, gravitational force

Answer:

The stovetop system is open because heat can be lost into the air. A closed system is one that cannot transfer energy to its surroundings.

Answer: Butter paper, ground glass, and a bonus thin sheets of plastic

Explanation: Translucent objects allow light to pass through them partially.

Answer:

Tinted windows, frosted glass, sunglasses, wax paper, fingers, and certain plastics are all examples of translucent objects. Translucent is defined as a material that blurs light as it passes through.

Hope this helps :)

Answer:

The average speed form A to C is 72 miles/hour

Explanation:

Average Speed

If an object travels a distance d in a time t regardless of the direction, the average speed is the quotient of the distance over the time:

[tex]\displaystyle \bar v=\frac{d}{t}[/tex]

Lily travels from A to C in two steps:

First, she takes ta=3 hours from A to B at va=60 miles/hour. The distance traveled in that time is:

da=va*ta

da=3*60 = 180

da = 180 miles

Then she takes tb=2 hours to travel from B to C at a speed 50% increased with respect to va, thus:

vb=150*va/100=1.5*60=90

vb=90 miles/hour

She travels a distance:

db=2*90=180 miles

The total distance traveled is

dt=180 + 180 = 360 miles

And the total time taken is

tt= 3 + 2 = 5 hours

Thus, the average speed is:

[tex]\displaystyle \bar v=\frac{dt}{tt}[/tex]

[tex]\displaystyle \bar v=\frac{360}{5}[/tex]

[tex]\displaystyle \bar v=72\ miles/hour[/tex]

The average speed form A to C is 72 miles/hour

Protection in a volcanic ashfall:

Stay inside, if possible, with windows and doors closed.

Wear long-sleeved shirts and long pants.

Use goggles to protect your eyes.

Keep your car or truck engine switched off.

Protection from earthquake if you're indoors:

Drop down and take cover under a desk or table

Stay inside until the shaking stops and it is safe to exit.

Stay away from bookcases and other furniture that can fall on you.

Stay away from windows and light fixtures.

If you are in bed – hold on and stay there.

Answer:

best way is to remain inside ur home or under any table

The answer (distance) is:

The distance of the truck in the given time is 216 m.

Displacement (s) of an object equals, velocity (u) times time (t), plus ½ times acceleration (a) times time squared (t2). Use standard gravity, a = 9.80665 m/s2, for equations involving the Earth's gravitational force as the acceleration rate of an object.

Multiply the acceleration by time to obtain the velocity change: velocity change = 6.95 * 4 = 27.8 m/s . Since the initial velocity was zero, the final velocity is equal to the change in speed. You can convert units to km/h by multiplying the result by 3.6: 27.8 * 3.6 ≈ 100 km/h.

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Answer:

Would it be starting point?

Explanation:

When you start a sport or something, you may not be good or bad at it. However, as time goes on you are going to improve.

Idk if this helps or not buh yeah

Answer:

Speed is a way of measuring how quickly something is moving or being done, or something moving fast. An example of speed is a car being driven 45 miles per hour. An example of speed is someone cleaning a room in 10 minutes.

Answer:

29.36 [tex]m/s[/tex] downwards

Explanation:

Use the equation [tex]v^{2} =u^{2} +2as[/tex]

Choose upwards as positive

v=?

u= 57sin31 (vertical component of initial velocity)

a= -9.8

s=0

[tex]v^{2} = (57sin31)^2 +2(-9.8)(0)[/tex]

v=29.36 [tex]m/s[/tex] downwards

Answer: Weight is a measure of the force of gravity pulling down on an object. It depends on the object's mass and the acceleration due to gravity, which is 9.8 m/s2 on Earth. The formula for calculating weight is F = m × 9.8 m/s2, where F is the object's weight in Newtons (N) and m is the object's mass in kilograms.

Answer:gravity pulling down on an object

Explanation:

Answer:

v=u+at

v=8+(4x2)

v=16m\s2

Definition: Wavelength can be defined as the distance between two successive crests or troughs of a wave.

Answer: Moving the hand farther away from the door knob

Explanation:

The magnetic force becomes weaker when there is more distance

The magnetic force becomes weaker when there is more distance.

The nucleus and electrons are drawn to one another by the electric force. The void created by a positive or negative charge is referred to as an electric field since it generates a field there.

If you had a positive charge just here, it would have an electric field surrounding it and affect the area in which it was located.

The same applies for a negative charge; it too has an electric field surrounding it. Now, opposite charges attract each other while like charges repel one another. A positive charge here and a positive charge here, for example, would resist one another since they are similar charges.

Therefore, The magnetic force becomes weaker when there is more distance.

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Answer:

1 lb. is 453.592 grams

Explanation:

1lb is 453.592 grams

1/Rt = 1/R1 + 1/R2 + 1/R3+ 1/R4+ 1/R5

1/Rt = 1/6+ 1/6+1/6+1/6+1/6

1/Rt = 5/6

Rt = 6/5

Rt = 1.2 ohm

so B is the answer

Answer:

D. The number of cattle ranchers decreased in the past five years

Explanation:

According to Jennifer M Schieltz and Daniel I Rubenstein (2016), "More than a quarter of earth's land surface is used for grazing domestic livestock." This has negative effects on availability of pasture for herbivorous wildlife such as the deer.

Increase in the number of cattle  ranchers decreases the availability of pasture and vice versa.

Hence, the decrease in the number of cattle ranchers over the past five years led to an increase in the deer population due to a decrease in competition for pasture.

Answer:

I think is B. sound, nuclear, electrical

but if I wrong then I am so sorry

Answer:

0.36 kgm/s

Explanation:

Formula for momentum is :

P=mv

p is momentum

m is mass = 30g = 0.03kg

v is velocity = 12 m/s

P= 0.03 x 12

P = 0.36 kgm/s

Answer:

The answer is B.

Explanation:

Because that's the one that's more-so higher up than the other soccer balls. This grants the ball to have higher potential energy than the rest.

Quote:

"Your body is as weak as your soul, so it is easy to separate the two."

- Akuma

The ball b would have the greatest amount of the potential energy as the mass of each ball is the same then the ball on the highest altitude would have the greatest amount of the potential energy contained with it.

Mechanical energy is the combination of all the energy in motion represented by total kinetic energy and the total stored energy in the system which is represented by total potential energy.

The mechanical energy = potential energy + kinetic energy

As given in the problem, the image here shows four soccer balls at four different locations on an uneven soccer field very near sea level.

The potential energy of the ball = mass×gravity×height

Since each ball's mass is the same, the ball at the highest altitude would have the most potential energy within it. As a result, ball b would have the greatest quantity of potential energy.

Thus,the correct answer is option A.

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Answer: From spectral lines astronomers can determine not only the element, but the temperature and density of that element in the star.

Explanation: The spectral line also can tell us about any magnetic field of the star. The light from the stuff between the stars allows astronomers to study the interstellar medium.

Hope this helps! :)

Answer:

Reversible change from one state to another

Hope this helps

:)

Answer:

12s

Explanation:

Answer:

What class is this for, I think I have done this before.

Answer:

[tex]q_1=\pm0.03 \mu C[/tex] and [tex]q_2=\pm0.02 \mu C.[/tex]

Explanation:

According to Coulomb's law, the magnitude of  force between two point object having change [tex]q_1[/tex] and [tex]q_2[/tex] and by a dicstanced is

[tex]F_c=\frac{1}{4\pi\spsilon_0}\frac{q_1q_2}{d^2}-\;\cdots(i)[/tex]

Where, [tex]\epsilon_0[/tex] is the permitivity of free space and

[tex]\frac{1}{4\pi\spsilon_0}=9\times10^9[/tex] in SI unit.

Before  dcollision:

Charges on both the sphere are [tex]q_1[/tex] and [tex]q_2[/tex], d=20cm=0.2m, and [tex]F_c=1.35\times10^{-4}[/tex] N

So, from equation (i)

[tex]1.35\times10^{-4}=9\times10^9\frac{q_1q_2}{(0.2)^2}[/tex]

[tex]\Rightarrow q_1q_2=6\times10^{-16}\;\cdots(ii)[/tex]

After dcollision: Each ephere have same charge, as at the time of collision there was contach and due to this charge get redistributed which made the charge density equal for both the sphere t. So, both have equal amount of charhe as both are identical.

Charges on both the sphere are mean of total charge, i.e

[tex]\frac{q_1+q_2}{2}[/tex]

d=20cm=0.2m, and [tex]F_c=1.406\times10^{-4}[/tex] N

So, from equation (i)

[tex]1.406\times10^{-4}=9\times10^9\frac{\left(\frac{q_1+q_2}{2}\right)^2}{(0.2)^2}[/tex]

[tex]\Rightarrow (q_1+q_2)^2=2.50\times10^{-15}[/tex]

[tex]\Rightarrow q_1+q_2=\pm5\times 10^{-8}[/tex]

As given that the force is repulsive, so both the sphere have the same nature of charge, either positive or negative, so, here take the magnitude of the charge.

[tex]\Rightarrow q_1+q_2=5\times 10^{-8}\;\cdots(iii)[/tex]

[tex]\Rightarrow q_1=5\times 10^{-8}-q_2[/tex]

The equation (ii) become:

[tex](5\times 10^{-8}-q_2)q_2=6\times10^{-16}[/tex]

[tex]\Rightarrow -(q_2)^2+5\times 10^{-8}q_2-6\times10^{-16}=0[/tex]

[tex]\Rightarrow q_2=3\times10^{-8}, 2\times10^{-8}[/tex]

From equation (iii)

[tex]q_1=2\times10^{-8}, 3\times10^{-8}[/tex]

So, the magnitude of initial charges on both the sphere are [tex]3\times10^{-8}[/tex] Coulombs[tex]=0.03 \mu C[/tex] and [tex]2\times10^{-8}[/tex] Colombs or [tex]0.02 \mu C[/tex].

Considerion the nature of charges too,

[tex]q_1=\pm0.03 \mu C[/tex] and [tex]q_2=\pm0.02 \mu C.[/tex]

Answer:

60

Explanation: