28. A car is traveling east at an unknown initial velocity. Without changing directions, it accelerates at 0.75 m/s²
for a distance of 300 m, increasing its velocity to 30 m/s. What was the initial velocity of the car?

The number 43,700 cm when written by the use of the scientific notation will be written as 4.37 * 10^4 cm.

The scientific notation involves writing a number in such a way that it does not involve a lot of digits. This methods helps us to save space that would have been used to write long digits.

Hence, the number 43,700 cm when written by the use of the scientific notation will be written as 4.37 * 10^4 cm.

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6.64 minutes to heat 0.71kg of water from 20°C to its boiling point using a 600W microwave.

To calculate the time it takes to heat the water, we can use the formula:

Q = mcΔT

where Q is the heat energy absorbed by the water, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.

First, let's find the change in temperature:

ΔT = boiling point - room temperature = 100°C - 20°C = 80°C

Next, we can calculate the heat energy absorbed:

Q = mcΔT = (0.71kg)(4200J/kgK)(80°C) = 239,040J

Now, let's find the time it takes to supply this amount of energy using a 600W microwave:

Power (P) = Energy (Q) / Time (t)

t = Q / P = 239,040J / 600W = 398.4 seconds

Therefore, it will take approximately 398.4 seconds or 6.64 minutes to heat 0.71kg of water from room temperature to its boiling point using a 600W microwave.

It's worth noting that this calculation assumes all the microwave's power is effectively transferred to the water and that there are no heat losses during the process. In practice, factors like heat transfer efficiency and losses should be considered, which may slightly affect the actual heating time.

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The velocity of the red ball after the collision is m/s is  11. 125 m/s

The conservation of momentum states that, inside some hassle domain, the quantity of momentum stays regular; momentum is neither created nor destroyed, but handiest modified thru the action of forces as defined via Newton's legal guidelines of motion.

Calculation:-

Given,

M =  0.5-kg

V i = 10 m/s

M₂ =  0.4 kg

V i  = 0

V f = 1.1 m/s

V f = ?

M₁V₁ + M₂V₂ = V f M₁ + V f M₂

 = 0.5 × 10 + 0.4 ×0  = 1.1 × 0.5 + V f × 0.4

= 5 = 0.55 + 0.4 V f

V f = 5 -  0.55/0.4

    = 4.45 / 0.4

   = 11. 125 m/s

The law of conservation of momentum states that in an isolated machine the whole momentum of two or extra our bodies performing upon each different remains regular unless an outside pressure is applied. therefore, momentum can neither be created nor destroyed.

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The energy lost to friction and air resistance is 186 J.

option B.

The energy lost to friction and air resistance is calculated from the change in the mechanical energy of the pendulum.

The initial potential energy of the pendulum at the initial position is calculated as;

PEi = mghi

where;

P.Ei = 12 kg x 9.8 m/s² x 20 m

P.Ei = 2,352 J

The final kinetic energy of the pendulum is calculated as follows;

K.Ef = 0.5 x 12 kg x (19 m/s)²

K.Ef = 2,166 J

ΔE = 2,166 J - 2,352 J

ΔE = -186 J

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The minimum mass required to be placed on the 0.00 cm mark of the meter stick to maintain equilibrium is 0.120 kg.

To maintain equilibrium, the torques acting on the meter stick must balance each other. The torque is given by the formula:

τ = r * F * sin(θ)

where τ is the torque, r is the distance from the pivot point to the point where the force is applied, F is the force applied, and θ is the angle between the force vector and the lever arm.

In this case, the meter stick is in equilibrium when the torques on both sides of the pivot point cancel each other out. The torque due to the weight of the meter stick itself is acting at the center of mass of the meter stick, which is at the 50.0 cm mark.

Let's denote the mass to be placed on the 0.00 cm mark as M. The torque due to the weight of M can be calculated as:

τ_M = r_M * F_M * sin(θ)

where r_M is the distance from the pivot point to the 0.00 cm mark (which is 30.0 cm), F_M is the weight of M, and θ is the angle between the weight vector and the lever arm.

Since the system is in equilibrium, the torques on both sides of the pivot point must be equal:

τ_M = τ_stick

r_M * F_M * sin(θ) = r_stick * F_stick * sin(θ)

Substituting the given values:

30.0 cm * F_M = 20.0 cm * (0.0400 kg * 9.8 m/s^2)

Solving for F_M:

F_M = (20.0 cm / 30.0 cm) * (0.0400 kg * 9.8 m/s^2)

F_M = 0.0264 kg * 9.8 m/s^2

F_M = 0.25872 N

Finally, we can convert the force into mass using the formula:

F = m * g

0.25872 N = M * 9.8 m/s^2

M = 0.0264 kg

Therefore, the minimum mass required to be placed on the 0.00 cm mark of the meter stick to maintain equilibrium is 0.120 kg.

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Answer:

Work done W = 750 J

Explanation:

Given:

Force applied F = 50 N

Distance s = 15 m

Find:

Work done W

Computation:

Work done W = Force x distance

Work done W = 50 x 15

Work done W = 750 J

Answer:

W = 750 J

Explanation:

the person on top is correct

Answer:

12 cm/s

Explanation:

Quite simply, you are looking for  cm/s

  so   60 cm / 5s   = 12 cm/s

Answer:

12 cm/second

Explanation:

To calculate the speed of an object, simply obtain the distance traveled by the ball and divide it by the total time it took to travel 60 centimeters.

⇒ Distance/Time = Speed

In this case, the ball traveled 60 centimeters in 5 seconds.

Therefore, the speed of the ball is;

60 centimeters (Distance)/5 seconds (Time) = 12 cm/second

To find the mass of the object, we can use the formula for kinetic energy:

Kinetic energy (KE) = (1/2) * mass * velocity^2

Given that the kinetic energy is 426 J and the velocity is 13 m/s, we can rearrange the equation to solve for the mass:

mass = (2 * KE) / (velocity^2)

Substituting the given values:

mass = (2 * 426 J) / (13 m/s)^2

mass = (2 * 426 J) / (169 m^2/s^2)

mass = 852 J / 169 m^2/s^2

mass = 5.04 kg

Therefore, the mass of the object is 5.04 kg.

Elements combine to form compounds. The correct answer is A.

Elements combine with each other in chemical reactions to form compounds. A compound is a substance composed of two or more different elements chemically combined in a fixed ratio by mass. For example, water is a compound composed of hydrogen and oxygen in a fixed ratio of 2:1 by mass.

B. Molecules are formed when two or more atoms combine chemically, but these atoms can be of the same element or different elements. For example, oxygen gas (O2) is a molecule composed of two oxygen atoms.

C. Atoms are the smallest unit of matter that retains the properties of an element. Atoms do not combine to form other atoms or compounds.

D. Mixtures are composed of two or more substances physically mixed together, but the substances retain their individual properties and can be separated by physical means. Mixtures are not formed by the chemical combination of elements. Examples of mixtures include air and saltwater.

Therefore, The correct answer is option A.

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Since the car is accelerating at a constant rate, the distance it travels during each second of its motion will be directly proportional to the time it has been accelerating.

In the first second, the car moved a distance of 2 meters, and in the second second, it will move twice the distance of the first second, so the car will move additional distance of 2*2 = 4 meters during the second second of its motion.

The distance traveled during the second second of its motion is 1/2 * 2 = 1 meters.

A car that accelerates at a constant rate will move a distance equal to the initial velocity multiplied by time plus 1/2 the acceleration multiplied by the square of time. Since the car starts from rest, the initial velocity is zero.

Therefore, the distance traveled during the second second is 1/2 * acceleration \(* (time)^2 = 1/2 * a * t^2 = 1/2 * a * 1^2 = 1/2 * a\) Since the car moved 2.0 meters in the first second, it means the acceleration is\(2m/s^2\), and the distance traveled during the second second is 1/2 * 2 = 1 meters.

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Answer:

trueeeeeeee..........mmmm...........

Answer:

42.1%

Explanation:

Applying,

E(%) = (M.A/V.R)×100............. Equation 1

Where E(%) = Percentage efficiency, M.A = mechanical advantage, V.R = Velocity ratio.

But,

M.A = L/E............... Equation 2

Where L = Load, E = Effort.

From the question,

Given: L = 150 N, E = 200 N

Substitute these values into equation 2

M.A = 200/150

M.A = 1.33

Also,

V.R for Inclined plane = 1/sin∅ =

V.R = 1/sin∅............... Equation 2

Where ∅ = angle of the inclined plane.

Where,

tan∅ = 4/12

∅ = tan⁻¹(4/12)

∅ = 18.43°

Therefore,

V.R = 1/sin18.43

V.R = 3.16.

Substituting the value of M.A and V.R into equation 1

E(%) = (1.33/3.16)×100

E(%) = 42.1%

The answer for this question is D

Answer:

Explanation:

A. in

According to the Keynesian view, manipulating foreign sector spending is not a reliable way to move the U.S. economy toward a more acceptable equilibrium because it does not address the fundamental causes of economic instability.

Keynesian economics focuses on the role of domestic demand in driving economic growth and stability. The government can use fiscal and monetary policy to stimulate aggregate demand and promote full employment. However, changes in foreign sector spending can be unpredictable and beyond the control of domestic policymakers. For instance, an increase in foreign demand for U.S. exports could boost economic growth and employment in the short run, but it may not be sustainable if the foreign demand later decreases. Similarly, a decrease in foreign demand for U.S. exports could have negative short-term effects on the economy, but it may not necessarily lead to a long-term decline. In short, Keynesian economics emphasizes the importance of domestic demand management and stabilizing the economy through government intervention. While changes in foreign sector spending can have some impact on the economy, they are generally seen as unreliable and unpredictable, and therefore not a reliable tool for achieving economic stability in the long run.

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Answer:

920000

Explanation:

Each kg contains 1,000 grams

This question is incomplete, the complete question is;

Super fine 40-gauge copper wire has a diameter of only 0.080 mm and weighs only 44.5 g/km. Suppose a spool of 40-gauge wire weighs 205 g less after some wire is pulled off to wind a magnet. How could you calculate how much wire was used ?

Answer: length of wire to be used is 4.6067 km

Explanation:

Circular diameter = d mm

Linear mass density of wire = μ g/km

let m be the mass of wire un-winded from spool to wind a magnet.

If M is mass of wire initially

then

Δm = M - m  { which represents decrease of mass }

Also if L rep the length of wire pulled off,

then

Δm = μ × L grams

⇒ L = Δm/μ km

now given that weight Δm = 205 g and length per unit weight μ = 44.5 g/km

we substitute

L = 205 g  / 44.5 g/km

L =  4.6067 km

Therefore length of wire to be used is 4.6067 km

The total distance covered by the car is 300 miles.

The total displacement covered by the car is zero.

The average speed of the car is 17.88 m/s.

The average velocity of the car is also zero.

Distance between the points A and B, d = 150 miles

Time taken by the car to travel from A to B, t₁ = 3 hours

Time taken by the car to travel from B to A, t₂ = 5 hours

a) Given that the car travelled from A to B and then back to A.

Therefore, the total distance covered by the car is,

Distance = 2 x d

Distance = 2 x 150

Distance = 300 miles

Since the car is travelling from A to B and then returning back to the initial point A, the total displacement covered by the car is zero.

b) The speed with which the car travelled from A to B is,

v₁ = d/t₁

v₁ = 150/3

v₁ = 50 miles/hr

v₁ = 22.35 m/s

The speed with which the car travelled from B to A is,

v₂ = d/t₂

v₂ = 150/5

v₂ = 30 miles/hr

v₂ = 13.41 m/s

Therefore, the average speed of the car is,

v = (v₁ + v₂)/2

v = (22.35 + 13.41)/2

v = 17.88 m/s

As, the total displacement of the car is zero, the average velocity of the car is also zero.

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Answer: Static electricity is the build up of an electrical charge on the surface of an object. It's called "static" because the charges remain in one area rather than moving or "flowing" to another area.

Explanation:

A.30cm

B.282.7cm/s

C.26655cm/s²

Explanation:

A. Maximum displacement= Amplitude= 0.3m

B.mum velocity=

2πAf= 2π x 1.5x30 =282.7cm/s

C. Maximum acceleration

= ( angular velocity)² A= (2πf)² A

=( 2 x 3.142 x 1.5)² x 30

2665.5cm/s²

Answer:

Biochar is produced by heating biomass in the total or partial absence of oxygen. Pyrolysis is the most common technology employed to produce biochar, and also occurs in the early stages of the combustion and gasification processes. Besides biochar, bio-oil and gas can be collected from modern pyrolysers.

Answer:

The tension on the string is  \(T = 43.302 \ N\)

Explanation:

From the question we are told that

    The mass of the rock is \(m_r = 5.00 \ kg = 5000 \ g\)

       The density of the rock is \(\rho = 4300 \ kg/m^3 = 4.3 g/dm^3\)

Generally the volume of the rock is mathematically evaluated as

          \(V = \frac{m_r}{\rho}\)

substituting values

        \(V = \frac{5000}{4.3}\)

       \(V = 1162.7 \ dm^3\)

The volume of the rock immersed in water is

      \(V_w = \frac{V}{2}\)  

substituting values

     \(V_w = \frac{1162.7 }{2}\)

     \(V_w = 581.4 \ dm^3\)

mass of water been displaced by the this volume is

     \(m_w = V_w\)     According to Archimedes principle

=>   \(m_w = 581.4 \ g\)

     \(m_w = 0.5814 \ kg\)

The weight of the water displace is  

      \(W _w = m_w * g\)

      \(W _w = 0.5814 * 9.8\)

      \(W _w = 5.698 \ N\)

The actual weight of the rock is  

      \(W_r = m_r * g\)

     \(W_r = 5.0 * 9.8\)

     \(W_r = 49.0 \ N\)

The tension on the string is

       \(T = W_r - W_w\)

substituting values

       \(T = 49.0 - 5.698\)

       \(T = 43.302 \ N\)

The correct answer is : B. The air above the land heats up and cools off more quickly than the air over water is the most important factor that creates wind patterns.

This is because temperature differences between land and water create differences in air pressure, which in turn causes the movement of air (wind). During the day, land heats up faster than water, causing the air above the land to rise and cooler air to flow in from over the water, creating a sea breeze. At night, the opposite happens, with the land cooling off faster than the water and creating a land breeze. These temperature differences and resulting wind patterns can also be influenced by the geography and topography of the surrounding area.

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Answer:

The value is  \(v = 0.3133 \ m/s\)

Explanation:

From the question we are told that

     The mass  of the first  model is  \(m_1 = 0.235 \ kg\)

      The sliding speed is \(u_1 = 0.720 \ m/s\)  

       The mass of the second model is  \(m_2 = 0.305 \ kg\)

Generally from the law of momentum conservation w have that

                \(m_1 * u_1 + m_2 * m_2 * u_2 = (m_1 + m_2 ) v\)

Here \(u_2\) is the velocity of the second model and given that it is  motionless at it initial state the value will be  \(u_2 = 0 \ m/ s\)

 So  

                \(0.235 * 0.720 + 0.305 * 0 = (0.235 + 0.305 ) v\)

=>              \(v = 0.3133 \ m/s\)

Answer: wqcjn qefveqeqfbj qeib

Explanation:oiaer vgneiofrvn eiforbnewtjbioe

Answer:

d) Rest and motion are relative

Explanation:

rest and motion are relative

The independent variable that we have in the experiment is the temperature. Option B

We know that if we are talking about an experiment, what we have to look at is that we must consider the interplay of the variables that is taking place in the process. As we change one of the variables in the experiment, there would be a change in another variable in the experiment also.

Now, the variable that we usually beging to alter is the one that we call the independent variable. As we change the value of this particular variable, there would be a change in the independent variable.

We have been told that; a  student conducts an experiment to test how the temperature affects the amount of salt that can dissolve in water.

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Answer:

A) 1000 kg

Explanation:

vf = vi + at

0 = 20 + (a)(10)

a = -2.0 m/s^2

F = ma

2000 = (m)(2)

m = 1000 kg

Answer:

a) t1 = v0/a0

b) t2 = v0/a0

c) v0^2/a0

Explanation:

A)

How much time does it take for the car to come to a full stop? Express your answer in terms of v0 and a0

Vf = 0

Vf = v0 - a0*t

0 = v0 - a0*t

a0*t = v0

t1 = v0/a0

B)

How much time does it take for the car to accelerate from the full stop to its original cruising speed? Express your answer in terms of v0 and a0.

at this point

U = 0

v0 = u + a0*t

v0 = 0 + a0*t

v0 = a0*t

t2 = v0/a0

C)

The train does not stop at the stoplight. How far behind the train is the car when the car reaches its original speed v0 again? Express the separation distance in terms of v0 and a0 . Your answer should be positive.

t1 = t2 = t

Distance covered by the train = v0 (2t) = 2v0t

and we know t = v0/a0

so distanced covered = 2v0 (v0/a0) = (2v0^2)/a0

now distance covered by car before coming to full stop

Vf2 = v0^2- 2a0s1

2a0s1 = v0^2

s1 = v0^2 / 2a0

After the full stop;

V0^2 = 2a0s2

s2 = v0^2/2a0

Snet = 2v0^2 /2a0 = v0^2/a0

Now the separation between train and car

= (2v0^2)/a0 - v0^2/a0

= v0^2/a0