An object is released from rest at a height H near and above the surface of Earth. As the object falls toward the surface, Earth’s atmosphere exerts a resistive force on the object such that it reaches a terminal velocity before it reaches the ground. Which of the following claims is true? Select two answers.


The system consisting of only the object is an open system.

The system consisting of only the object is an open system.
A

Earth’s atmosphere does negative work on the object as it falls toward the surface.

Earth’s atmosphere does negative work on the object as it falls toward the surface.
B

The change in the object’s kinetic energy from the instant it is released from rest, to the instant it reaches terminal velocity, is zero.

The change in the object’s kinetic energy from the instant it is released from rest, to the instant it reaches terminal velocity, is zero.
C

The total mechanical energy of the object-Earth system remains constant at all times in which the object is in motion.

Answer: The focal length of the lens = 3.32 cm.

Explanation:

Lens formula : [tex]\dfrac1f=\dfrac1v-\dfrac1u[/tex]    (i)

f= focal length , v=image distance , u =object distance.

magnification: m = [tex]\dfrac{v}{u}[/tex]   (ii )

Given: v= -12.8 cm , m =2.85

Put values in (ii), we get

[tex]2.85=\dfrac{-12.8}{u}\\\\\Rightarrow\ u=\dfrac{-12.8}{2.85}\\\\\Rightarrow\ u=-4.49\ cm[/tex]

substitute values of u , v in (i)

[tex]\dfrac1f=\dfrac1{-12.8}-\dfrac{1}{4.49}\\\\\Rightarrow\dfrac1f=-0.30084214922\\\\\Rightarrow\ f=\dfrac{-1}{-0.30084214922}\approx3.32\ cm[/tex]

Hence, the focal length of the lens = 3.32 cm.

Answer:

6.92

Explanation:

2.85=-(-12.8/x)

do=4.49

1/f= 1/4.49 + 1/-12.8

f=6.92

Answer:

[tex]m_2=6.3\:\mathrm{kg}[/tex]

Explanation:

In a perfectly elastic collision, the total kinetic energy of the system is maintained. Therefore, we can set up the following equation:

[tex]\frac{1}{2}m_1{v_1}^2+\frac{1}{2}m_2{v_2}^2=\frac{1}{2}m_1{v_{1'}}^2+\frac{1}{2}m_2{v_{2'}}^2[/tex]

Since the second block was initially at rest, [tex]\frac{1}{2}m_2{v_2}^2=0[/tex].

Plugging in all given values, we have:

[tex]\frac{1}{2}m_1{v_1}^2=\frac{1}{2}m_1{v_{1'}}^2+\frac{1}{2}m_2{v_{2'}}^2,\\\\\frac{1}{2}\cdot4.4\cdot9.2^2=\frac{1}{2}\cdot 4.4 \cdot (-2.5)^2+\frac{1}{2}\cdot m_2\cdot 6.7^2,\\m_2=\fbox{$6.3\:\mathrm{kg}$}[/tex].

Answer:  momentum is determined and conserved.

Answer:

monument is determined

Answer:

Explanation:

The capacitor is of parallel plate capacitor type

Capacitance C = ε₀ A / 4π d

ε₀  is 8.85 x 10⁻¹² , A  is plate area and  d is distance between plate .

d = 1.7 cm

C = 8.85 x 10⁻¹² x π x (6.5 x 10⁻² )² / 4π x 1.7 x 10⁻²

= 55 x 10⁻¹⁴F .

Charge on each electrode = C x V , V is voltage of battery .

= 55 x 10⁻¹⁴ x 14

= 770 x 10⁻¹⁴ C  

Electric field strength = V / d where V is potential difference of battery , d is distance between plate .

= 14 / 1.7 x 10⁻²

= 8.23 x 10² V / m

The potential difference between plate

= potential difference of the battery

= 14 V .

Explanation:

Elements are distinct substances that cannot be split-up into simpler substances. These substances consist of only one kind of atom.

There are over one hundred elements known to date. Each of these elements is usually symbolized by a capital letter or a capital letter followed by a small letter derived from English or Latin or Greek name of the element concerned.

Elements can be categorized in different ways.

Atoms are the smallest unit of elements that takes part in a chemical reaction.

Answer:

The answer is I

Explanation:

Answer:

4.) l, ll, and lll only

Explanation:

The rest of the answers:

1.) The field energy will increase.

2.) The energy increases, and the lines of force are denser.

3.) It points toward the field of earths magnetic poles.

5.) ll, lV, l, lll

Explanation:

From the experiment:

      Number of protons  = 74

      Number of neutrons  = 110

Number of protons in an element is the atomic number of the element. It is used to locate and position and element on the periodic table.

For a neutral or uncharged atom, the number of protons is the same as the number of electrons.

The element whose number of protons or atomic number if 74 is Tungsten

  Mass number  = 74 + 110  = 184g/mol

Answer:

a) mv(final):<0,0,0> minus mv(initial):<25,0,0> = <-25,0,0>

b) mv(final):<25,0,0> minus mv(initial):<0,0,0> = <25,0,0>

c) conservation of momentum makes it <0,0,0>

for a-b-c, momentum_system + momentum_surroundings = 0

Explanation:

Hope this helps

The velocity of each ball after the collision is 1.75 m/s

Law of conservation of momentum states that:

Total momentum before collision = Total momentum after collision

m₁u₁ + m₂u₂ = (m₁ + m₂)v

Where m₁, m₂ is the mass of object, u₁, u₂ is the initial velocity before collision and v is the final velocity after collision

Given that: m₁ = m₂ = 0.25 kg, u₁ = 3.5 m/s, u₂ = 0, hence:

0.25(3.5) + 0.25(0) = (0.25 + 0.25)v

v = 1.75 m/s

The velocity of each ball after the collision is 1.75 m/s

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Answer:

10. 65 N

11. 35 N

Explanation:

10. Determination the force that sends the soccer ball towards the goal.

We'll begin by calculating the acceleration of the ball. This can be obtained as follow:

Initial velocity (u) of the ball = 0 m/s

Final velocity (v) of the ball = 32.5m/s time (t) = 0.21 s

Acceleration (a) of the ball =?

a = (v – u) /t

a = (32.5 – 0) / 0.21

a = 32.5 / 0.21

a = 154.76 m/s²

Finally, we shall determine the force that sends the soccer ball towards the goal. This can be obtained as follow:

Mass (m) of the ball = 0.42 kg

Acceleration (a) of the ball = 154.76 m/s²

Force (F) =?

F = ma

F = 0.42 × 154.76

F = 65 N

Thus, the force that sends soccer ball towards the goal is 65 N

11. Determination of the force exerted by the rocket on the satellite.

We'll begin by calculating the acceleration of the satellite. This can be obtained as follow:

Initial velocity (u) of satellite = 0 m/s

Final velocity (v) of satellite = 0.63 m/s

Time (t) = 1296 s

Acceleration (a) of the satellite =?

a = (v – u) /t

a = (0.63 – 0) / 1296

a = 0.63 / 1296

a = 4.861×10¯⁴ m/s²

Finally, we shall determine the force exerted by the rocket on the satellite. This can be obtained as follow:

Mass (m) of the satellite = 72000 Kg

Acceleration (a) of the satellite = 4.861×10¯⁴ m/s²

Force (F) =?

F = ma

F = 72000 × 4.861×10¯⁴

F = 35 N

Thus, the force exerted by the rocket on the satellite is 35 N

Answer:

a)   d = 12 km, d = 0,  b)  v = 0.4 km / min, v = 0,  c) v = 0

Explanation:

This problem asks to find the distance and the displacement. We must emphasize that the distance is a scalar and the displacement is a vector quantity

In the exercise, the bold letters indicate vectors

a) Let's find the total distance of the trip

           d = d₁ + d₂

where d₁ is the distance to get to the flowers and d₂ is the distance to return to the hive from the flowers

             d₁ = d₂ = 6 km

             d = 12 km

we look for the displacement that is a vector quantity

          d = d₁ - d₂

since the second displacement is in the opposite direction of the first

          d = 0

b) the average speed of the trip, again this magnitude is a scalar

          v = d / t

distance is d = 12 km t total time is t = 15 + 15 = 30 min

          v = 12/30

          v = 0.4 km / min

average velocity (vector) of the entire travel, in that case the displacement is zero

          v = 0

c) If the path is not a straight line but the time is the same, the average speed cannot be calculated since it lacks the distance value

In the same case to calculate the average velocity that is a vector, it will be zero since the net displacement is zero

            v = 0

Answer:

The ice will melt

Heat flows from the water to the ice

Explanation:

If we add a lump of ice to a tumbler containing water, the ice lump will melt in the water.

This is a simple physical change of state from solid to liquid.

At the end both the solid ice and the original liquid maintains the liquid state.

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:

a) θ = 58.3º

b) vfh = 13.7 m/s

c) g = -9.8 m/s2

d) h = 22.2 m

e) vfb = 15.5 m/s

Explanation:

a)

        [tex]x_{f} = v_{ox} * t = v_{o} * cos \theta * t (2)[/tex]

        [tex]cos \theta = \frac{x_{f} }{v*t} = \frac{41.0m}{26.0m/s*3.00s} = 0.526 (3)[/tex]

b)

c)

d)

       [tex]\Delta y = v_{oy} * t - \frac{1}{2} *g*t^{2} (6)[/tex]

       [tex]\Delta y = 22.1 m/s* 3.0s - \frac{1}{2} *9.8m/s2*(3.00s)^{2} = 22.2 m (8)[/tex]

e)

       [tex]v_{fy} = v_{oy} - g*t (9)[/tex]

       [tex]v_{fy} = 22.1 m/s - 9.8m/s2*3.00s = -7.3 m/s (10)[/tex]

       [tex]v_{f} = \sqrt{(13.7m/s)^{2} +(-7.3m/s)^{2}} = 15.5 m/s (11)[/tex]

Answer:

f" = 40779.61 Hz

Explanation:

From the question, we see that the bat is the source of the sound wave and is initially at rest and the object is in motion as the observer, thus;

from the Doppler effect equation, we can calculate the initial observed frequency as:

f' = f(1 - (v_o/v))

We are given;

f = 46.2 kHz = 46200 Hz

v_o = 21.8 m/s

v is speed of sound = 343 m/s

Thus;

f' = 46200(1 - (21/343))

f' = 43371.4285 Hz

In the second stage, we see that the bat is now a stationary observer while the object is now the moving source;

Thus, from doppler effect again but this time with the source going away from the obsever, the new observed frequency is;

f" = f'/(1 + (v_o/v))

f" = 43371.4285/(1 + (21.8/343))

f" = 40779.61 Hz

Answer:

CuCl₂   +    H₂S    →    CuS   +    2HCl  

Explanation:

The unbalanced reaction expression is given as;

        CuCl₂   +    H₂S    →    CuS   +    HCl

The problem here involves balancing of chemical equations.

 We use a mathematical approach to solve this problem. Here assign coefficients a, b, c and d as values that will effect the balance;

          aCuCl₂   +    bH₂S    →    cCuS   +    dHCl

Conserving Cu:  a  = c

                     Cl:   2a  = d

                     H: 2b  = d

                     S: b  = c

let a  = 1; c  = 1, b  = 1 and d  = 2

         CuCl₂   +    H₂S    →    CuS   +    2HCl  

Answer: This means that the objects didn't hold or have any charges before it was charged by something or someone

Explanation:

Like a dead phone it dosn't have any "charge", but after you put the charger in the wall you can plug the phone in and get it charged It's an on going cycle of energy being turned into other energy.

Answer:

The answer is C

Explanation:

The positive and negative charges are equal.

Answer:

30 degrees

Explanation: reflection, same angle

For a ray of monochromatic light is incident on a plane mirror at and angle of 30°. The angle of reflection for the light is 30°.

Reflection occurs when radiation bounces off from a surface. Light is an electromagnetic wave and it can be reflected. According to the laws of reflection, the angle of incidence is equal to the law of reflection.

Hence, for a ray of monochromatic light is incident on a plane mirror at and angle of 30°. The angle of reflection for the light is 30°.

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Answer:

B.

Explanation:

From the given information, since the capacitors are disconnected from the battery, the electric field between the plate does not change due to the fact that there is no difference in charge density.

Hence, the potential difference after separating the plates is:

V' = Ed

V = e (2d')

V' = 2V

For the energy stored in the capacitor;

[tex]U' = \dfrac{1}{2}QV'[/tex]

where;

V' = 2V

[tex]U' = \dfrac{1}{2} Q (2V)}[/tex]

[tex]U' =2( \dfrac{1}{2} Q V)[/tex]

U' = 2U

Thus, in the capacitor, the energy that is being stored is doubled.

Answer:

b. U = Q - W

Explanation:

Given;

change in internal energy, ΔU = 36 kJ

heat transferred to the surroundings Q  = 14 kJ

Apply first law of thermodynamic; the change in internal energy is equal to heat added to the system minus work done by the system.

ΔU = Q - W

Since heat was lost to surroundings, Q = - Q

ΔU = (-Q) - W

36 kJ = -14 kJ - W

36 kJ + 14 kJ = - W

50 kJ = - W

W = - 50 kJ (the negative sign shows that work has been done on the system)

Thus, 50 kJ of work is done on the system.

The only correct answer in the given options is "b" U = Q-W

Answer:

20 J

Explanation:

Work done is given force by distance .

W= F * d  where F is force given by the product of pressure and area

W= P* Δv  where Δv  is change in volume.

Given that ;

1 mole of an ideal gas is kept at 0°C, the pressure of the gas is : 1 atm.

Δv  is change in volume , 30 l - 10l = 20 l

W= 1 * 20 = 20 J

Answer:

Emec = 94050 [J]

Explanation:

In order to solve this problem, we must understand that all thermal energy is converted into mechanical energy.

The thermal energy can be calculated by means of the following expression.

[tex]Q=m*C_{p}*(T_{final}-T_{initial})[/tex]

where:

Q = heat [J]

Cp = specific heat of water = 4186 [J/kg*°C]

m = mass = 300 [g] = 0.3 [kg]

T_final = 95 [°C]

T_initial = 20 [°C]

Now we can calculate the heat, replacing the given values:

[tex]Q=0.3*4180*(95-20)\\Q= 94050[J][/tex]

Since all this energy must come from the mechanical energy delivered by the exercise bike, and no energy is lost during the process, the mechanical energy must be equal to the thermal energy.

[tex]Q=E_{mec}\\E_{mec}=94050[J][/tex]

Answer:

1796.48 m

Explanation:

Given that :

First part of journey :

Initial Velocity, u = 0

Acceleration, a, = 1.60 m/s²

Time, t = 14 s

Distance traveled, S = 0.5at²

S = 0.5 * 1.60 * 14²

S1 = 156.8m

2nd part :

Speed is constant

Time = 70 seconds

At constant speed ;

Distance = speed * time

Speed, V = u + at

V = 0 + 1.6*14

V = 22.4 m/s

Distance, S2 = 22.4 * 70 = 1568 m

3rd part :

Deceleration = - 3.50m/s²

Final velocity, v = 0

Time taken to attain rest

V = u + at

0 = 22.4 - 3.5(t)

3.5t = 22.4

t = 22.4/3.5

t = 6.4 seconds

S3 = ut - 0.5at² (deceleration)

S3 = (22.4*6.4) - 0.5(3.5)*6.4^2

S3 = 71.68m

S1 + S2 + S3

156.8m + 1568m + 71.68m

= 1796.48 m

Answer:

The period of the swing depends on only the length of the string and not on the mass of the bob and the period of the pendulum depends on only the horizontal component of g.

Explanation:

The period of the swing depends on only the length of the string and not on the mass of the bob. Since the length of the string and the mass of the bob define the pendulum.

Also, the properties that define the motion are the component of the weight of the bob in the horizontal direction which determines the to and fro movement of the bob. So, the period of the pendulum depends on only the horizontal component of g.

So, T = 2π√(l/g) where l = length of pendulum and g = acceleration due to gravity.

Answer:

Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi), and one complete orbit takes 365.256 days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi).

Explanation:

Explanation:

Every object has a center of gravity. ... The force of gravity acting on an object is directed through this center of gravity and toward the center of the earth. The object's weight, W, can be represented by a vector directed down (along the line the object would fall if it were dropped).

It should be towards the center of the earth.

The following information should be considered:

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Answer:

B

Explanation:

8-2 is 6

times that times 8 u get B

Answer:

Explanation:

Let t represent the time for Tina to catch David.

Hence, considering the equation of linear motion S = ut + 1/2at^2..... 1

For David u = 28.0 m/s where 'a' is set to nought

S = ut

S = 28t.......2

For Tina consider equation 1

Where acceleration = 2.90m/s^2 and u is set at nought

S = 1/2×2.90 m/s×t^2.......3

Equate 2 and 3

28t = 1.45t^2

Divide through by t

28 = 1.45t

t = 28/1.45

t = 19.31seconds

Now put the value of t into equation 3

S = 1/2×2.90 m/s×t^2.......3

= 1.45×20×20

= 580m

Tina must have driven 580meters before passing David

Considering the equation of linear motion : V^2 = U^2+2as

Where u is set at nought

V^2 = 2as

V^2 = 2×2.9×580

V^2 = 3364

V = √3364

V = 58m/s

Her speed will be 58m/s

(a) Tina should drive for 580 m, before passing the David.

(b) The speed of Tina during her passage through the David is 58 m/s.

Given data:

The initial velocity of the David is, u = 28.0 m/s.

The magnitude of acceleration is, [tex]a = 2.90 \;\rm m/s^{2}[/tex].

(a)

We can use the second kinematic equations of motion to obtain the distance covered by Tina, before passing the David. As per the second kinematic equation of motion,

[tex]s= u't + \dfrac{1}{2}at^{2}[/tex]

Here, u' is the initial speed of Tina and t is the time interval. Then,

Let t represent the time for Tina to catch David.

Hence, considering the equation of linear motion as,

S = ut + 1/2at²...............................................................(1)

Also,

S = ut

S = 28t ...........................................................................(2)

For Tina consider equation 1

S = 1/2×2.90t²................................................................(3)

Equate 2 and 3

28t = 1.45t²

 28 = 1.45t

t = 28/1.45

t = 19.31 seconds

Now put the value of t into equation (3)

S = 1/2×2.90 t².

   = 1.45×20×20

   = 580m

Thus, we can conclude that Tina should drive for 580 m, before passing the David.

(b)

Now, using the third kinematic equation of motion to obtain the speed of Tina during her passage through David as,

v² = u²+2as

Solving as,

v² = 28.0² + 2(2.90)(580)

v = √3364

v = 58m/s

Thus, we can conclude that the speed of Tina during her passage through the David is 58 m/s.

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Answer:

its b for sure

Explanation:

Answer:

B. It might be accessed by someone who was not the intended

recipient

Answer:

C. both have same K.E

Explanation:

Momentum can be defined as the multiplication (product) of the mass possessed by an object and its velocity. Momentum is considered to be a vector quantity because it has both magnitude and direction.

Mathematically, momentum is given by the formula;

[tex] Momentum = Mass * Velocity [/tex]

Kinetic energy can be defined as an energy possessed by an object or body due to its motion.

Mathematically, kinetic energy is given by the formula;

[tex] K.E = \frac{1}{2}MV^{2}[/tex]

Where, K.E represents kinetic energy measured in Joules.

M represents mass measured in kilograms.

V represents velocity measured in metres per seconds square.

Both momentum and kinetic energy are related to the velocity of an object or a body.

Since the horse and a dog have same momentum. Thus, they both have same kinetic energy.