If the force of gravity suddenly stopped acting on planets, they would

A.) spiral slowly towards the sun

B.) continue to orbit the sun

C.) move in straight lines tangent to thier orbits

D.) spiral slowly away from the sun

E.) fly straight away from the sun

Answer:

Half life refers to the time for 1/2 of the radioactive atoms to decay.

Suppose that X has a half life of 10 days and Y has a half life of 20 days

If both start out with 1000 radioactive atoms then after 20 days

X would have 250 radioactive atoms and Y would have 500 atoms

The rate of decay is greater for the shorter half life:

In the example given X  must have the smaller rate of decay because it has a longer half life.

Answer:

8.34 x 10⁻⁶N

Explanation:

Given parameters:

Mass 1  = 100kg

Mass 2 = 200kg

Distance of separation  = 40cm = 0.4m

Unknown:

Gravitational force of attraction between them  = ?

Solution:

To solve this problem, we use the expression below which is derived from the Newton's law of universal gravitation:

           Fg  = [tex]\frac{G x mass 1 x mass 2}{d^{2} }[/tex]

G is the universal gravitation constant = 6.67 x 10⁻¹¹

d is the separation

 Now;

  Fg = [tex]\frac{6.67 x 10^{-11} x 100 x 200}{0.4^{2} }[/tex]   = 8.34 x 10⁻⁶N

Answer:

C. A heat engine must deposit some energy in a cold reservoir.

Explanation:

The second law of thermodynamics says that "It is impossible to extract an amount of heat Q from a hot reservoir and use it all to do work W. Some amount of heat q must be exhausted to a cold reservoir."

This means that if we extract an amount of heat Q from the hot reservoir, the work W can never be exactly equal to Q, then there is a surplus of heat q that must be deposited in a cold reservoir.

Then we have the equation:

Q = W + q

From this we can conclude that the correct option is:

C. A heat engine must deposit some energy in a cold reservoir.

There will be always some energy that is not transformed into work, and is deposited in a cold reservoir.

C. A heat engine must deposit some energy in a cold reservoir.

Therefore, option C is correct.

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Answer:

5 Km/h

Explanation:

From the question given above, the following data were obtained:

Distance travelled = 10 Km

Time = 2 hours

Speed =?

Speed is simply defined as the distance travelled per unit time. Mathematically, it can be represented as:

Speed = distance travelled /time.

With the above formula, we can obtain the speed at which the duck is travelling as follow:

Distance travelled = 10 Km

Time = 2 hours

Speed =?

Speed = distance travelled /time.

Speed = 10 / 2

Speed = 5 Km/h

Thus, the duck is travelling at a speed of 5 Km/h

Answer:

0.25 kg

Explanation:

p = mv

2 = m(8)

2/8 = m(8)/8 *cancels

m = 1/4 OR 0.25 kg

Answer:

See the answer below

Explanation:

The elastic potential energy can be calculated by means of the following equation:

[tex]E_{el}=\frac{1}{2} *k*x^{2}[/tex]

where:

Eel = elastic energy = 1500 [J]

k = spring constant = 45000 [N/m]

x = extension [m]

[tex]1500=\frac{1}{2} *45000*x^{2} \\3000=45000*x^{2} \\x=\sqrt{0.06666}\\x=0.258[m] = 25.8 [cm][/tex]

Answer:

reducing temperature of the surrounding

Explanation:

combustion reactions are exothermic so they give off heat. reducing the temperature of the surrounding will enable more efficient energy transfer

Answer:

(a) The two balls collide [tex]2\; \rm s[/tex] after launch.

(b) The height of the collision is [tex]4\; \rm m[/tex].

(Assuming that air resistance is negligible.)

Explanation:

Let vector quantities (displacements, velocities, acceleration, etc.) that point upward be positive. Conversely, let vector quantities that point downward be negative.

The gravitational acceleration of the earth points dowards (towards the ground.) Therefore, the sign of [tex]g[/tex] should be negative. The question states that the magnitude of [tex]g\![/tex] is [tex]10\; \rm m \cdot s^{-2}[/tex]. Hence, the signed value of [tex]\! g[/tex] should be [tex]\left(-10\; \rm m \cdot s^{-2}\right)[/tex].

Similarly, the initial velocity of the ball thrown downwards should also be negative: [tex]\left(-8.0\; \rm m \cdot s^{-1}\right)[/tex].

On the other hand, the initial velocity of the ball thrown upwards should be positive: [tex]\left(12\; \rm m \cdot s^{-1}\right)[/tex].

Let [tex]v_0[/tex] and [tex]h_0[/tex] denote the initial velocity and height of one such ball. The following SUVAT equation gives the height of that ball at time [tex]t[/tex]:

[tex]\displaystyle h(t) = \frac{1}{2}\, g \cdot {t}^{2} + v_0 \cdot t + h_0[/tex].

For both balls, [tex]g = \left(-10\; \rm m \cdot s^{-2}\right)[/tex].

For the ball thrown downwards:

[tex]\displaystyle h(t) = -5\, t^{2} + (-8.0)\, t + 40[/tex] (where [tex]h[/tex] is in meters and [tex]t[/tex] is in seconds.)

Similarly, for the ball thrown upwards:

[tex]\displaystyle h(t) = -5\, t^{2} + 12\, t[/tex] (where [tex]h[/tex] is in meters and [tex]t[/tex] is in seconds.)

Equate the two expressions and solve for [tex]t[/tex]:

[tex]-5\, t^{2} + (-8.0)\, t + 40 = -5\, t^{2} + 12\, t[/tex].

[tex]t = 2[/tex].

Therefore, the collision takes place [tex]2\, \rm s[/tex] after launch.

Substitute [tex]t = 2[/tex] into either of the two original expressions to find the height of collision:

[tex]h = -5\times 2^{2} + 12 \times 2 = 4\; \rm m[/tex].

In other words, the two balls collide when their height was [tex]4\; \rm m[/tex].

The time the two balls collide is 0.4 seconds while the height at which they collide is 4m

The given parameters are :

Initial Velocity U = 8m/s

Height H = 40m

For the second ball, the initial velocity = 12m/s

a.) For the first ball, the height attained at the point of collision will be

h = ut + 1/2gt^2

h = 8t + 1/2 x 10t^2 ........ (1)

For the second ball, the height attained at the point of collision will be

h = 12t - 1/2 x 10t^2 .........(2)

Since the height will be the same for the two balls, equate the two equations

8t + 10t^2 = 12t - 10t^2

Collect the like term

8t - 12t = -5t^2 - 5t^2

-4t = -10^2

10t = 4

t = 4/10

t = 0.4s

b.) Substitute time t in any of the equation to find the height

h = 12(0.4) - 0.5 x 10(0.4)^2

h = 4.8 - 0.8

h = 4m

Therefore, the time the two balls collide is 0.4 seconds while the height at which they collide is 4m

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Answer:

[tex] \underline{ \boxed{ yes}}\\[/tex]

Explanation:

[tex]given : initial \: velocity \: (u )= 40 {ms}^{ - 1} \\ given : final \: velocity \: (u )= 0 {ms}^{ - 1} \\ given : - (acceleration) \: (a_r) = 2 {ms}^{ - 2} \\ given : distance \: (s) \: = \: ? : \\ but \: {v}^{2} = {u}^{2} + 2( a)s\\ {0}^{2} = {40}^{2} + 2( - 2)s \\ - {40}^{2} = - 4s \\ s = \frac{ - {40}^{2} }{ - 4} \\ s = \frac{1600}{4} \\s = 400 \: m[/tex]

Answer:

[tex]0.15\: \mathrm{Hz}[/tex]

Explanation:

The frequency is of an object is given by [tex]f=\frac{1}{T}[/tex], where [tex]T[/tex] is the orbital period of the object.

Since the racecar makes 24 revolutions around a circular track in 162 seconds, it will take the racecar [tex]\frac{162}{24}=6.75\:\mathrm{s}[/tex] per revolution.

Therefore, the frequency of the racecar is [tex]\frac{1}{6.75}=\fbox{$0.15\:\mathrm{Hz}$}[/tex] (two significant figures).

The radius of the track is irrelevant in this problem.

Answer:

B

Explanation:

on edge

The illustration with a vector pointed right going through an opening in a boundary and turning into a transverse wave on the other side demonstrates the phenomenon of absorption, so, option B is correct.

Absorption, in wave motion, is the process by which a wave's energy is transferred to matter when the wave travels through it. The energy of an electromagnetic, acoustic, or other wave is related to the square of its amplitude, which is the maximum displacement or movement of a point on the wave.

The amplitude of a wave continuously diminishes as it travels through a substance. The medium is described as being transparent to a specific type of radiation if just a tiny portion of the energy is absorbed, whereas it is described as opaque if all the energy is lost.

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#SPJ2

Answer: E =  7,490.6 N/C

Explanation:

If we have a field E, and a particle with a charge q, the force that the particle experiences is:

F = E*q

In this case, we know that the force is:

F = 1.2*10^(-15) N

And we know that the particle is a proton, where the charge of a proton is:

q = 1.602*10^(-19) C

Then we can replace these two values in the equation to get:

1.2*10^(-15) N = E*1.602*10^(-19) C

We just need to isolate E.

(1.2*10^(-15) N)/(1.602*10^(-19) C) = E

7,490.6 N/C = E

That is the strength of the electric field.

Answer:

7.01yard/sec

Explanation:

Given parameters:

Initial position  = 50yard

Final position = 12yard

Time  = 5.42s

Unknown:

Average speed of runner  = ?

Solution:

To solve this problem;

        Speed  = [tex]\frac{distance}{time}[/tex]  

Distance covered  = Initial position  - final position  = 50 - 12  = 38yards

So;

       Speed  = [tex]\frac{38}{5.42}[/tex]   = 7.01yard/sec

Answer:

[tex]12\:\mathrm{N}[/tex]

Explanation:

Force is given by the equation [tex]F=ma[/tex].

Plugging in given values, we have:

[tex]F=ma=2.6\cdot 4.5=11.7=\fbox{$12\:\mathrm{N}$}[/tex] (two significant figures).

Answer:

  Natalie says that all things with mass have a gravitational field, but the force is very weak and cannot be perceived around small objects.

Explanation:

The force due to gravity is proportional to the mass of the object and inversely proportional to the square of the distance between objects. The Earth is so massive that the force due to its gravity is much greater than the force between objects on the counter.

If there were no friction, the objects might move toward each other, depending on what other masses were near them tending to cause them to move in other directions.

Natalie's explanation is about the best.

__

Additional comment

The universal gravitational constant was determined by Henry Cavendish in the late 18th century using lead balls weighing 1.6 pounds and 348 pounds. His experiment was enclosed in a large wooden box to minimize outside effects. While these masses are somewhat greater than those of a glue bottle and stapler, the experiment shows the force of gravity between "small" objects can be measured.

Answer:

0.025J

Explanation:

Kinetic energy = ½ × Mass × velocity²

0.20÷1000=0.0002

½ × 0.0002 × 15.8²=0.024964J

Answer:  Choice A) 2 meters per second

=======================================================

Explanation:

The smaller ball has momentum of

p = m*v

p = (1 kg)*(4 m/s)

p = 4 kg*m/s

All of this momentum transfers into the larger ball because the smaller ball comes to a complete stop.

For the larger ball, we have p = 4 and m = 2. Let's find v.

p = m*v

4 = 2*v

4/2 = v

2 = v

v = 2 m/s which is why the answer is choice A

The larger ball moves at a speed of 2 meters per second. The speed is cut in half compared to the smaller ball because the larger ball has more inertia (aka more mass), and therefore it takes more energy to move it. If you apply the same energy to each, then the smaller object moves faster.

Answer:

A)5524J,

B) 29.2Nm

Explanation:

This question can be treated using work- energy theorem

Work= change in Kinectic energy

W= Δ KE

Work= difference between the final Kinectic energy and intial Kinectic energy.

We know that

Kinectic energy= 1/2 mv^2 .............eqn(1)

This can be written in term of angular velocity, as

KE= 1/2 I

Answer: b. Electrons move from glass to silk

Explanation:

When the glass rod is rub over against the silk, the glass loses the electrons due to the physical contact with the silk and the friction so produced.  The surface of the glass becomes positively charged and the surface of the silk becomes negatively charged. As the surface of the glass loses electrons which are accepted by the silk surface.

Answer: b

Explanation:

Answer:

12.31 m/s

Explanation:

If we recall from the previous knowledge we had about speed,

we will know that:

speed = distance/ time.

As such:

The average speed of the rider bicycle is

average speed = total distance/ total time

Mathematically, it can be computed as:

[tex]v_{avg} = \dfrac{d+d}{\dfrac{d}{v_1}+ \dfrac{d}{v_2}}[/tex]

[tex]v_{avg} = \dfrac{2d}{\dfrac{d}{10 \ m/s}+ \dfrac{d}{16 \ m/s}}[/tex]

[tex]v_{avg} = \dfrac{2}{\dfrac{1}{10 \ m/s}+ \dfrac{1}{16 \ m/s}}[/tex]

[tex]v_{avg} = \dfrac{2}{\dfrac{13}{80 \ m/s}}[/tex]

[tex]\mathbf{v_{avg} =12.31 \ m/s}[/tex]

Answer:

15 seconds

Explanation:

If car was moving at 20m/s for 3 sec.

if car traveled 100m = 15 sec total

Explanation:

Given that,

A girl walks 20.0 m east then 70.0 meters north.

Displacement is the shortest path covered by an object. Let it is d. It is calculated as :

[tex]d=\sqrt{20^2+70^2} \\\\=72.80\ m[/tex]

For direction,

[tex]\theta=\tan^{-1}(\dfrac{70}{20})\\\\\theta=74.05^{\circ}[/tex]

Girl's distance = 20 m + 70 m

= 90 m

Hence, this is the required solution.

Answer:

[tex]375\:\mathrm{N}[/tex]

Explanation:

Work is given by the equation [tex]W=F\Delta x[/tex]. Plugging in given values, we get:

[tex]W=75\cdot 5=\fbox{$ 375\:\mathrm{N}$}[/tex].