Physics College

## Answers

**Answer 1**

**Answer: **207 W

** Explanation: **I assumed here that the object is moved vertically. If that is the case, the work done on the object is equal to its change in gravitational potential energy:

where

m = 47 kg is the mass of the object

g = 9.8 m/s^2 is the acceleration of gravity

is the change in height

Substituting,

Now we can calculate the power used, which is given by

Hope this helps I'm sorry if i'm wrong but I tried :(

## Related Questions

A force of 10 newtons toward the right is exerted on a

wooden crate initially moving to the right on a horizontal

wooden floor. The crate weighs 25 newtons.

1. Calculate the magnitude of the force of friction between the crate and the floor.

2. What is the magnitude of the net force acting on the crate?

### Answers

**Answer:**

**Explanation:**

coefficient of kinetic friction of wooden floor μ = .4

force of friction = μ R , R is reaction force of floor

R = mg = weight of body

R = 25 N

force of friction = .4 x 25 = 10 N

Net force on the crate = 10 - 10 = zero .

Net force on the body will be nil.

A transformer has an output coil with 6 times as many turns as the input coil. If the input frequency is f then the output frequency will be:_______

a. 9f

b. 6f

c. 1/6 f

d. f

### Answers

**Answer:**

d. f

**Explanation:**

Based on the principle of operation of transformer, when a.c voltage is applied at the terminal of the primary coil (input coil), an alternating magnetic flux is produced in the iron core which links the secondary coil (output coil).

Also, an alternating e.m.f of * the same frequency* as that of primary coil (input coil) will be induced in the secondary coil (output coil) by mutual inductance.

Thus, If the input frequency is "f" then the output frequency will be "f" (since the frequency will be the same).

The correct option is "D"

Once ignited, a small rocket motor on a spacecraft exerts a constant force of 10 N for 7.80s. During the burn the rocket causes the 100-kg craft to accelerate uniformly. Determine that acceleration

### Answers

**Answer:**

a = 0.01 [m/s²]

**Explanation:**

To solve this problem we must use Newton's second law, which says that the sum of forces on a body is equal to the product of mass by acceleration.

ΣF = m*a

where:

F = forces = 10 [N]

m = mass = 100 [kg]

a = acceleration [m/s²]

10 = 100*a

a = 0.01 [m/s²]

When a box is placed on an inclined surface with no friction, it will:

### Answers

**Answer: With no friction, the box will accelerate down the ramp**

**Explanation:**

It will gain speed down the ramp

go to his profile and roast the mess out of him plzz 403665fl 50 points

### Answers

**Answer:**

ok

**Explanation:**

A wheel turns through 5.5 revolutions while being accelerated from rest at 20rpm/s.(a) What is the final angular speed ? (b) How long does it take to turn the 5.5 revolutions?

### Answers

**Answer:**

(a) The final angular speed is **12.05 rad/s**

(b) The time taken to turn 5.5 revolutions** **is **5.74 s**

**Explanation:**

Given;

number of revolutions, θ = 5.5 revolutions

acceleration of the wheel, α = 20 rpm/s

number of revolutions in radian is given as;

θ = 5.5 x 2π = 34.562 rad

angular acceleration in rad/s² is given as;

[tex]\alpha = \frac{20 \ rev}{min} *\frac{1}{s} *(\frac{2\pi \ rad}{1 \ rev } *\frac{1 \ min}{60 \ s}) \\\\\alpha = 2.1 \ rad/s^2[/tex]

(a)

The final angular speed is given as;

[tex]\omega _f^2 = \omega_i ^2 + 2\alpha \theta\\\\\omega _f^2 = 0 + 2\alpha \theta\\\\\omega _f^2 = 2\alpha \theta\\\\\omega _f = \sqrt{2\alpha \theta}\\\\ \omega _f = \sqrt{2(2.1) (34.562)}\\\\ \omega _f = 12.05 \ rad/s[/tex]

(b) the time taken to turn 5.5 revolutions** **is given as

[tex]\omega _f = \omega _i + \alpha t\\\\12.05 = 0 + 2.1t\\\\t = \frac{12.05}{2.1} \\\\t = 5.74 \ s[/tex]

A motobike's tire rotates with a constant angular speed of 62.8 rad/s. The radius of a tire is 30cm. Assuming that no slipping occurs, the number of

revolutions of the tire in one second is:

a.

12.6

b.

20

C.

18.8

d.

10

### Answers

Answer:

10

Explanation:

Given that :

Angular speed (w) = 62.8 rad/s

Radius of tire (r) = 30 cm

Number of revolutions per second :

s = 2πr

s = 2π * 0.3 = 1.8849555

The number or revolutions per second :

θ = s / r

θ = 1.884955 / 0.3

θ = 6.283185 rad

Number of revolutions per second :

62.8 / 6.283185

= 9.9949309

= 10

A 6.0-kg object moving at 5.0 m/s collides with and sticks to a 2.0-kg object. After the collision the composite object is moving at 2.0 m/s in a direction opposite to the initial direction of motion of the 6.0-kg object. Determine the speed of the 2.0-kg object before the collision. a. 23 m/s b. 15 m/s c. 11 m/s d. 8.0 m/s e. 7.0 m/s

### Answers

**Answer:**

**a) 23 m/s**

**Explanation:**

Assuming no external forces acting during the collision, total momentum must be conserved, as follows:

[tex]p_{o} = p_{f} (1)[/tex]

The initial momentum p₀, can be written as follows:

[tex]p_{o} = m_{1} * v_{1o} + m_{2}* v_{2o} = 6.0 kg * 5.0 m/s + 2.0 kg * v_{2o} (2)[/tex]

The final momentum pf, can be written as follows:

[tex]p_{f} = (m_{1} + m_{2} )* v_{f} = 8.0 kg* (-2.0 m/s) (3)[/tex]

Since (2) and (3) are equal each other, we can solve for the only unknown that remains, v₂₀, as follows:

[tex]v_{2o} = \frac{-6.0kg* 5m/s -8.0 kg*2.0m/s}{2.0kg} = \frac{-46kg*m/s}{2.0kg} = -23.0 m/s (4)[/tex]

This means that the 2.0-kg object was moving at 23 m/s in a direction opposite to the 6.0-kg object, so its initial speed, before the collision, was 23.0 m/s.

The **speed **of the **2.0-kg** object before the **collision **will be **23 m/s.**Option** A** is correct.

What is the law of conservation of momentum?

According to the law of conservation of **momentum**, the **momentum **of the body before the **collision **is always equal to the **momentum **of the body after the **collision**.

The **given **data in the problem is;

**m₁** is the mass of objthe ct = 6.0-kg

**v₁** is the speed moving = 5

**m₂** is the mass of object 2 = 2.0 Kg

**V** is the final speed = 2.0 m/s

v₂ is the **speed **of the **2.0-kg** object before the **collision =?**

According to the law of conservation of **momentum**;

**Momentum **before collision =**Momentum **after collision

[tex]\rm m_1v_1 + m_2v_2 = V(m_1 + m_2)\\\\(6 \times 5) + (2 \times v_2) = -2.0 \times (8) \\\\ \rm v_2 = \frac{-46}{2.0} \\\\ \rm v_2 =-23.0\ m/sec[/tex]

Hence the **speed **of the **2.0-kg** object before the **collision **will be **23 m/s.**Option** A** is correct.

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Help me

An atomic nucleus suddenly bursts apart (fission) into two pieces. Piece A with mass mA travels to the left with a speed of vA. Piece B with mass mB travels to the right with speed vB. Show the velocity of piece B in terms of mA, mB and VA.

Solution:

Consider that the nucleus is not acted by an external force. Thus, momentum is conserved, so: pBf + pAf = 0

Substituting the expression for momentum results to

mBv (_______) + (_________) mAv (______) = 0

Deriving the expression for the velocity of piece B results to

v(_____) =(mA/m ______)vA

### Answers

**Answer:**

[tex]v_{B} = \frac{m_{A}v_{A}}{m_{B}}[/tex]

**Explanation:**

We can apply the law of conservation of momentum on the nucleus in its initial and final state of nucleus:

**Initial Momentum = Final Momentum**

**momentum of nucleus before bursting = momentum of piece A + momentum of Piece B**

[tex](m_{nucleus})(velocity of nucleus) = m_{A}v_{A} + m_{B}v_{B}\\[/tex]

since, nucleus was initially at rest. Therefore,

velocity of nucleus = 0 m/s

and due to opposite direction of forces:

Vb = - Vb

Therefore,

[tex](m_{nucleus})(0) = m_{A}v_{A} - m_{B}v_{B}\\\\m_{A}v_{A} = m_{B}v_{B}\\\\v_{B} = \frac{m_{A}v_{A}}{m_{B}}[/tex]

A piston above a liquid in a closed container has an area of 0.75m^2, and the piston carries a load of 200kg. What will be the external pressure on the upper surface of the liquid?

### Answers

**Answer:**

2613.3 pa

**Explanation:**

p=F/A

p=ma/A

p=200×9.8/0.75

p=2613.3

A machinist with normal vision has a near point at 25 cm. This machinist wears +4.25-diopter eyeglasses in order to do very close work. With these eyeglasses, what is the near point of the machinist?

a. 12 cm

b. 10 cm

c. 7 cm

d. 15 cm

e. 17 cm

### Answers

Answer: 12cm.

Explanation:

First we need to calculate the focal length which will be:

= 100 / 4.25

= 23.529

The near point of the machinist will be solved using the equation:

1/u + 1/v = 1/f

where,

v = -25

f = 23.529

1/u + 1/v = 1/f

1/u - 1/25 = 1/23.529

1/u = 1/23.529 + 1/25

u = 12.12cm

u = 12cm approximately

Therefore, the near point of the machinist is 12cm

The density for gold is 19.3 g/cm3. What would be the mass of a 45 cm3 piece of gold?

### Answers

**Answer:**

868.5 g

**Explanation:**

Mass= Density x Volume

Mass= 19.3 x 45

=868.5

**Answer:**

675.5g

**Explanation:**

The formula for density is: D = m/V.

To solve this problem, we need to rearrange this formula to solve for mass:

m = D x V.

Next, we plug the given values in for density, D, and volume, V:

m = 19.3 g/cm3 x 35 cm3

So, m = 675.5 g

Assume that the left side of your heart creates a pressure of 118 mm Hg by exerting a force directly on the blood over an effective area of 16.0 cm^2. What force does it exert to accomplish?

### Answers

**Answer:**

251.5 x 10⁻⁴ N

**Explanation:**

Pressure = Force / surface area

Force = pressure x area

pressure = 118 mm of Hg

= .118 x 13.6 x 9.8 N / m²

= 15.72 N / m ²

area = 16 x 10⁻⁴ m²

Force = 15.72 x 16 x 10⁻⁴

= 251.5 x 10⁻⁴ N .

How fast does water flow from a hole at the bottom of a very wide, 7.1 mm deep storage tank filled with water

### Answers

**Answer:**

The water will move faster

**Explanation:**

This happens as part of the consequences of the continuity of an incompressible fluid, of which water is an example.

so as the water emerges from the wider section the flow velocity increases and vice versa.

Hence the flow velocity in indirectly proportional to the area

The continuity equation is given below for our analysis

[tex]A1V1=A2V2\\[/tex]-------------------1

where

A1= the area of the wider section of the tank

V1= the flow velocity from the wider section

A2= the area of the hole at the bottom

V2= velocity of flow at the bottom.

A local AM radio station broadcasts at a frequency of 627 kHz. Calculate the wavelength at which it is broadcasting. Wavelength

### Answers

**Answer:**

Wavelength = 478.46 m

**Explanation:**

It is given that,

A local AM radio station broadcasts at a frequency of 627 kHz, f = 627000 Hz

We need to find the wavelength at which it is broadcasting. The wavelength is given by :

[tex]\lambda=\dfrac{c}{f}\\\\=\dfrac{3\times 10^8}{627\times 10^3}\\\\=478.46\ m[/tex]

So, the wavelength is 478.46 m.

In order for a protostar to transition to a full fledge star, what must happen? options: A. Nuclear fusion must occur in the protostar B. Planets must form around the protostar

C. The protostar must cool down D. Accretion must occur in the rings around the protostar

### Answers

We can see here that in order for a **protostar **to **transition **to a full fledge star, A. Nuclear fusion must occur in the protostar

What is protostar?

A **protostar **is a massive cloud of gas and dust in space that has the potential to become a star and is currently collapsing due to its own gravity. It is the initial stage of a star's development.

The **protostar **will continue to **collapse **and get hotter and denser until the conditions are right for nuclear fusion, when it will fuse and turn into a star.

A **star **gets its energy through nuclear fusion, which is the process of joining atomic nuclei to create heavier atoms. The star is not hot enough or thick enough during the protostar phase for nuclear fusion to take place.

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What's the temperature 414K in degrees Celsius?

### Answers

**Answer:**

212 I think

**Explanation:**

I looked it up

Millions of children are treated each year for sports-related injuries.

Is that True or False?

### Answers

**Answer:**

**True**

**Explanation:**

As per a survey conducted in the United States, it has been highlighted that among 30 million children participating in any sports, there are 3.5 million children who face injuries. It is because of these injuries that the children have to take some leave or absence from the sports. Also, the statistics discloses the fact that among all the injuries faced by the humans, one third of them are related to the childhood sports activities. Sprains and strains are among the most common of the injuries.

**Answer:**

true

**Explanation:**

edge

An object that weighs 2.450 N is attached to an ideal massless spring and undergoes simple harmonic oscillations with a period of 0.640 s. What is the spring constant of the spring

### Answers

The answer is B. 2.45 N/m.

A penny and a quarter are embedded in the concrete bottom of a swimming pool filled with water. Which of these coins experiences the greater downward force due to water pressure acting on it? Explain.

### Answers

**Answer: The quarter, because it has a larger surface area.**

**Explanation:**

remember the equation:

Pressure = Force/Area

Now, if we isolate Force, we get:

Force = Pressure*Area.

The pressure will be the same for both coins, but the area is not.

Then the one with a larger surface area will suffer a greater downward force. (We can consider the area as the area of the top or bottom of the coin)

The area of a circle of diameter d, is:

A = pi*(d/2)^2

where pi = 3.14

The penny has a diameter of 19.05 mm, then its area is:

A = 3.14*(19.05mm/2)^2 = 284.87mm^2

The quarter has a diameter of 24.26mm, then the area is:

A = 3.14*(24.26mm/2)^2 = 462 mm^2

Then the quarter has a larger area, this means that the quarter will experience the greater downward force due to water pressure.

A 100-turn coil has a radius of 7.50 cm and a resistance of 50.0 W. At what rate must a perpendicular magnetic field change to produce a current of 5.00 A in the coil

### Answers

**Answer:**

dB / dt = -141.47 T / s

**Explanation:**

For this exercise let's use Faraday's law to calculate the induced electromotive force

E = - N dФ / dt

the magnetic flux is

Ф = B. A

in this case the direction of the field and the normal to area are parallel so the scalar product is reduced to the algebraic product

Ф = B A

we substitute

E = - N A dB / dt

the area of the loop is

A = π r²

we substitute

E = - N π r² dB / dt

in the exercise indicate that the resistance of the coil is R = 50.0 Ω,

E = i R

we substitute

i R = -N π r² dB / dt

dB / dT = - i R / N π r²

let's calculate

dB / dt = - 5.00 50.0 / (100 π 0.075²)

dB / dt = -141.47 T / s

Arrange an 8-, 12-, and 16-Ω resistor in a combination that has a total resistance of 8.89 Ω pls with de work

### Answers

20 ohms in parallel with 16 ohm= 8.89

20x16/20+16. Product over sum

11. A 100-W incandescent light bulb has a cylindrical tungsten filament 30.0 cm long, 0.40 mm in diameter, and with an emissivity of 0.26. (a) What is the temperature of the filament

### Answers

**Answer:**

T = 556K

**Explanation:**

For this exercise let's use Stefan's law

P = σ A e T⁴

where the stafan-Boltzmann constant is 5,670 10⁻⁸ W / m² K⁴.

In this case the area of a circular cylinder is

A = π r²

the radius is

r = d / 2 = 0.150 m

A = π (0,150)²

A = 7.0685 10⁻² m²

let's clear

T⁴ = P /σ A e

T⁴ = 100 / (5.670 10⁻⁸ 7.0685 10⁻² 0.26)

T⁴ = 9.5966 10¹⁰ = 959.66 10⁸

T = 5.56 102 K

T = 556K

The** temperature of the filament** is **366.3 K**

Using the equation for radiated power, P

P = σεAT⁴ where **σ** = **Stefan-Boltzmann constant **= 5.67 × 10⁻⁸ W/m²K⁴, **ε** = **emissivity** = 0.26, **A **= **area of cylindrical tungsten filament** = πDh (since it radiates through its sides)where** D** =** diameter of tungsten filament** = 0.40 mm = 0.4 × 10⁻³ m and **h** = **length of tungsten filament** = 30.0 cm = 0.3 m and** T** = **temperature of tungsten filament.**

Since we require the **temperature of the filament**, making T subject of the formula, we have

**T = ⁴√(P/σεA)**

**T = ⁴√(P/σεπDh)**

Since P = 100 W, substituting the values of the variables into the equation, we have

T = ⁴√(P/σεπDh)

T = ⁴√(100 W/5.67 × 10⁻⁸ W/m²K⁴× 0.26 × π× 0.4 × 10⁻³ m × 0.3 m)

T = ⁴√(100 W/0.5558 W/K⁴ × 10⁻⁸)

T = ⁴√179.93 × 10⁸ K⁴)

T = 3.663 × 10² K

**T = 366.3 K**

So, the** temperature of the filament** is **366.3 K**

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What is the approximate efficiency of the engine?

A heat engine has a temperature of 1800 K. Some of the

heat from the engine flows to the surroundings, which

are at a temperature of 160 K.

0 16%

O 91%

O 103%

O 109%

### Answers

Answer:91% I think

Explanation:

The typical **engine **efficiency for a modern petrol combustion engine is from 20 to 30 percent. The remaining 70 to 80 percent of the heat energy of the petrol is **released **from the engine as friction loss, mechanical sound energy, or exhaust heat. Thus, option **B **is correct.

What approximate efficiency of the engine?

An engine's **efficiency **is measured by the heat **produced **divided by the amount of useful work done. Is the task complete. Is the task finished. Please be aware that the phrase “work done” refers to the force **applied **to the clutch or driveshaft.

Utilizing the following formula, **efficiency **may be represented as a ratio: output input. Output, often called work output, is the entire quantity of productive work completed, excluding **waste **and spoilage.

You may determine the **efficiency **by figuring out what proportion of the energy input results in the desired output: Efficiency is defined as **Energy **Out/Energy In 100%.

Therefore, This implies that the **work **produced by thermodynamic expansion is reduced by the friction and other **losses**.

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Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able 1) to push for 5.0 min longer. Compare the work they do. A) Both men do positive work, but Joel does 25% more work than Jerry. B) Both men do positive work, but Joel does 75% more work than Jerry. C) Both men do positive work, but Jerry does 50% more work than Joel. D) Both men do positive work, but Joel does 50% more work than Jerry E) Neither of them does any work.

### Answers

**Answer:**

the correct answer is E

**Explanation:**

Work is defined by the expression

W = **F. d**

Where the bold indicates vectors, we can make the dot product explicit

W = F d cos θ

We can see that this definition of work the two men apply a force, but the wall does not move, so if there is no displacement the work is zero.

When checking the correct answer is E

Suppose the spark plug on a heat engine is not functioning properly which statement best explains how this will affect the engine￼?

### Answers

**Answer:**

B. Burned gas...

**Explanation:**

The statement explains the importance of **enzymes **that check for and **repair** mistakes during **DNA replication** is the** enzymes **prevent many **genetic mutations** from being expressed.

What is RNA polymerase?

**RNA polymerase **is an **enzyme** that aids in the transcription of** DNA** into RNA during transcript in the **nucleus.** The** enzymes **prevent many **genetic mutations **from being **expressed.**

**Primase** is an** enzyme** that synthesizes short RNA sequences called primers. These primers serve as a starting point for DNA synthesis during replication as the** DNA polymerases **cannot begin the** synthesis** of the new strand, they only extend it after **primase** begins it and **primase **produces RNA molecules, the enzyme can be said to be a type of** RNA** **polymerase.**

Therefore, The statement explains the importance of **enzymes **that check for and **repair** mistakes during **DNA replication** is the** enzymes **prevent many **genetic mutations** from being expressed.

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A 200.0 kg sled is being towed horizontally with a force of 25 N for 120 m in 30 seconds. What is the power of the applied force?

### Answers

**Answer:**

.

**Explanation:**

If 400 N of force was applied to a rock and it had an acceleration of 20 ms2 , what is the mass of rock?

### Answers

**Answer:**

20 kg

**Explanation:**

The mass of the rock can be found by using the formula

[tex]m = \frac{f}{a} \\ [/tex]

f is the force

a is the acceleration

From the question we have

[tex]m = \frac{400}{20} = \frac{40}{2} \\ [/tex]

We have the final answer as

20 kg

Hope this helps you

From the 1780s to the late 1800s, people thought the amount of land and resources in the West was limited

### Answers

Answer:true

Explanation:

Imagine holding two identical bricks under water. Brick A is just beneath the surface of the water, while brick B is at a greater depth. What is the force needed to hold brick B in place? (Assume the density of water doesn't change with height.) a) the same as b) larger c) smaller than the force required to hold brick A in place.

### Answers

**Answer:**

I think it's c

**Explanation:**

The brick's mass, helps to hold it under the water but brick A is being held up. If you dropped the brick, it would sink to the bottom. You need a stronger force to hold it up.

Hope this helps you! x

**Buoyancy force **is needed to hold brick B in place.

What is force?

A **force **is an effect that can alter an object's motion according to physics. An object with mass can change its** velocity, or accelerate,** as a result of a force. An obvious way to describe force is as a push or a pull. A force is a vector quantity since it has both **magnitude and direction.**

Upthrust, often known as **buoyancy,** is an** upward force** applied by a fluid against the** weight **of an object that is partially or completely submerged. The** weight **of the fluid on top causes pressure in a fluid column to rise with depth.** **The brick's** mass**, helps to hold it under the water but brick A is being held up. If you dropped the brick, it would sink to the bottom. You need a stronger** force** to hold it up.

**Buoyancy force **is needed to hold brick B in place.

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