A child is stationary on a swing.(a)The child is given a push by his brother to start him swinging.His brother applies a steady force of 84 N over a distance of 0.25 m.(i) Calculate the work done by this force.(2)..............................................................................................................................................(ii) State how much energy is transferred by this force.(1)..............................................................................................................................................(iii) After several more pushes, the child has a kinetic energy of 71 J.The mass of the child is 27 kg.Show that the velocity of the child at this point is about 2.3 m/s.(2)(iv) Which one of these quantities changes in both size and direction while he is swinging?Put a cross ( ) in the box next to your answer.(1)Ahis gravitational potential energyBhis momentumCthe force of gravity acting on himDhis kinetic energy

Answers

Answer 1

Answer:

Work done = Fs

Explanation:

(i) W = Fxs

= 84N x0.25m

= 21 Joules

(ii) Ek = 1/2mv^2

71 = 1/2×27×v^2

71×2/27 = v^2

v = 23m/s

Answer 2

The work done by this force is 21 Joule.

Energy transferred by the force is 21 Joule.

The boy's momentum changes periodically, that is,  in both size and direction.

What is force?

An external force is an agent that has the ability to change the resting or moving condition of a body. It has a direction and a magnitude. So, it is  a vector quantity. Newton is the SI unit of force (N).

(i) Given parameter:

Steady force applied by his brother, F = 84 N.

Displacement, d = 0.25 m.

The work done by this force, W = F.d = 84×0.25 = 21 Joule.

(ii) Amount of work done is transferred by this force as an energy. So, amount of energy transferred by the force is 21 Joule.

(iii) Given parameter:

Mass of the child, m= 27 kg.

Kinetic energy, E = 71 J.

Let, velocity of the child = v, then kinetic energy is,

E = 1/2 × mv²

⇒ v = √(2E/m)

= √(2×71/27)

= 2.3 m/s.

Hence, the velocity of the boy is 2.3 m/s. (proved).

(iv) During swing, his velocity changes periodically. That's why, his momentum changes periodically, that is,  in both size and direction.

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Related Questions

. The gas in a piston (defined as the system) warms and absorbs 655 J of heat. The expansion performs 344 J of work on the surroundings. What is the change in internal energy for the system

Answers

The change in the internal energy for the system is 311 J

The change in internal energy for the system will be the difference between the heat absorbed and the work expansion from the surroundings.

i.e.

ΔU = Q + W

where;

internal energy = Uheat absorbed = Qworkdone on surroundings = -W

ΔU = ( 655 J + ( - 344 J) )

ΔU = 311 J

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Alejandro Kirk is the catcher for the Blue Jays’ baseball team. He exerts a forward force on the 0.145-kg baseball to bring it to rest from a speed of 38.2 m/s. During the process, his hand recoils a distance of 0.135 m.
Determine is the acceleration of the ball.
Determine the force applied by Alejandro.

Answers

Answer:

a= -5404.6 [m/s²]; F=785.75 [N].

Explanation:

1. Determine is the acceleration of the ball:

equation of the distance (0.135m) is:

[tex]S=-\frac{at^2}{2} +v_0t,[/tex]  where S=0.135[m]; a - required acceleration; t - elapsed time; v₀ - initial velocity (38.2 m/s);

also the required acceleration is:

[tex]a=\frac{v-v_0}{t}, where[/tex] V - the end velocity (0 m/s), t - elapsed time, ₀ - initial velocity (38.2 m/s).

Using the equations of reqruired acceleration and the distance it is possible to make up and solve the next system:

[tex]\left \{ {{a=-\frac{38.2}{t} } \atop {S=-\frac{at^2}{2}+38.2t }} \right. \ => \ \left \{ {{a=-\frac{38.2}{t} } \atop {0.5at^2-38.2t=0.135}} \right. \ => \ \left \{ {{a=-\frac{38.2}{t} } \atop {19.1t-38.2t=0.135}} \right. \ => \ \left \{ {{a=-5404.6} \atop {t=0.007}} \right.[/tex]

finally, a≈-5404.6 [m/s²].

2. Determine the force applied by Alejandro.

the energy is:

[tex]E=\frac{mv^2}{2}; \ or E=FS, where \ m-the \ mass; \ v-velocity; \ F-required \ force; S-distance;[/tex]

According to these two equations, the required force is:

[tex]F=\frac{E}{S}=\frac{mv^2}{2S};[/tex]

F=0.145*38.8²/2/0.135≈785.75 [N].

note, the suggested way is not the shortest one and not the only one.

P.S. if it is possible, check the arithmetic operations and the provided answers in other sources.

A 1,000 kg truck is traveling at 3 m/s. Suddenly, the driver sees a herd of cows on the road ahead and applies the brakes. The truck's tires could fail after doing 5,000 J of work to slow the vehicle. Can the truck stop before the tires fail?


A. Yes, the total KE the tires need to transfer out of the system is less than 5,000 J.


B. Yes, the tires do not do any work, it is only the brakes that do work.


C. No, the truck had to stop suddenly and the quick change in KE will cause the tires to fail.


D. No, the total KE the tires need to transfer out of the system is more than 5,000 J.

Answers

This question involves the concepts of the law of conservation of energy and kinetic energy.

The correct option is "A. Yes, the total KE the tires need to transfer out of the system is less than 5,000 J".

According to the law of conservation of energy:

Loss in Kinetic Energy = Work done by the tires

[tex]\frac{1}{2}mv^2=W[/tex]

where,

W = work done by tires = ?

m = mass of the truck = 1000 kg

v = speed of the truck = 3 m/s

Therefore,

[tex]W=\frac{1}{2}(1000\ kg)(3\ m/s)^2[/tex]

W = 4500 J

Since the failure limit of work done by the tire is 5000 J, which is greater than the actual work done by the tire in this scenario. Hence, the tire will not fail in this case.

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The attached picture explains the law of conservation of energy.

OK I have tried answering this for a while but im not very good at this so, how many waves will pass in 1 second if it has a frequency of 10 Hz?

Answers

Frequency means waves passing per second. So 10Hz means 10 waves passing a second

An object of mass of 2.0 kg rotates at constant speed in a horizontal circle of radius 5.0 m. The time
for one complete revolution is 3.0 s. What is the magnitude of the resultant force acting on the object.

Answers

Explanation:

follow the above attachment to get the answer.

foetus grows by receiving nutriens and oxygen from the mother. How does the foetus receive these nutriens and oxygen?​

Answers

Answer:

From the very beginning, the developing cells need oxygen and nutrients. The fetus receives its nutrition from the mother through the placenta and the umbilical cord.

Explanation:

If the coefficient of kinetic friction between the puck and the ice is 0.05, how far does the puck slide before coming to rest? Solve this problem using conservation of energy. initial speed is 5.3 m/s

Answers

Hi there!

We know that:

Ei = Ef

There is work being done on the object, so:

W = Force · displacement = F · d ⇒ work due to friction

KEi - Fd = KEf (0)

KEi = Fd

Input variables:

1/2mv² = μmgd

Cancel out the mass:

1/2v² = μgd

Solve for d:

1/2(5.3²)/(0.05 · 9.81) = 28.63 m

The gravitational field strength on Mars is 3. 7 N/kg. Kai has a mass of 55 kg. What would Kai weigh on Mars? Give your answer to 1 decimal place.

Answers

Hi there!

Weight = mass × acceleration due to gravity (or gravitational field strength)

We can write this as:

W = mg

Plug in the given values:

W = 55 × 3.7

W = 203.5 N

a box takes 350 N to start moving the coefficient of static friction is 0.35. what is the weight of the box?

Answers

Answer:

101.937 kg

Explanation:

The force needed to get the box moving must just cancel the static friction force:

F = µsmg  =  0.35•m•9.81 = 350 --->   m = 350 / (0.35•9.81) = 101.937 kg

Again, with units shown, and using 1 N = 1 kg•m/s2:

0.35•m•9.81(m/s2) = 350 N

solving for m:

m = 350 N / (0.35•9.81 m/s2)  =  (350 kg•m/s2) / (3.434 m/s2 ) = 101.937 kg

______________________

(Hope this helps can I pls have brainlist (crown)☺️

What is electromagnetic force and how does it work and what it does??

Answers

Answer:

Explanation:

The electromagnetic force, also called the Lorentz force, acts between charged particles, like negatively charged electrons and positively charged protons. Opposite charges attract one another, while like charges repel. The greater the charge, the greater the force.

najah, a management researcher, conducted an experiment with the goal of confirming or contradicting the behavioral leadership approach. najah spent many days following managers around while they worked. like the ohio state university and university of michigan studies, najah’s data showed that most managers focus on

Answers

Based on the information that is depicted from the question, the data from Najah showed that most managers focus on consideration and inspiration.

The behavioral leadership theory simply focuses on how leaders behave. The theory also assumes that other leaders copy each other's traits.

Based on the complete information, the data illustrated that most managers focus on consideration and inspiration. Managers inspire their subordinates in order to accomplish a goal.

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A 455 kg cannon fires a 21 kg cannonball at 26 m/s. If the cannon is on wheels, at what velocity does it move backward?

Answers

Answer:

A cannon ball of mass 4.0 kg is fired from a stationary 96 kg cannon at 120 m/s. Calculate the velocity of the cannon immediately after firing.

total momentum of cannon and cannon ball before = 0 kg m/s - because neither object is moving

total momentum of cannon and cannon ball after collision = 0 kg m/s - because momentum is conserved

Momentum of cannon ball after firing = 4.0 × 120 = 480 kg m/s.

Momentum of cannon after firing = -480 kg m/s (because it recoils in the opposite direction and 480 - 480 = 0 kg m/s, the total momentum after collision).

Rearrange p = m v to find v:

v = p/m

v = 480 divided by 96

v = 5.0 m/s

Note that the forward velocity of the cannon ball was given a positive value. The negative value for the cannon's velocity shows that it moved in the opposite direction.

how long does it take saturn to revolve around the sun

Answers

Answer: about 29.4 Earth years

Orbit and Rotation

One day on Saturn takes only 10.7 hours (the time it takes for Saturn to rotate or spin around once), and Saturn makes a complete orbit around the Sun (a year in Saturnian time) in about 29.4 Earth years (10,756 Earth days).

An object's inertia causes it to come to a rest position.

Answers

Answer:

no

Explanation:

the inertia of an object does not make it to come to rest, this is normally caused by friction

Power of an electric motor is 1 h.p. what does it mean ?​

Answers

Answer: HP = Horse Power.

Explanation: it is the unit given to tell the motor's particular power and 1hp = 746 watts.

DESPERATE!! WILL GIVE BARINLIST AND THANKS
Many farmers harvest their crops in the fall and then let the leftover plant material stay on the ground over winter. How does this help prevent erosion?

Answers

Answer:

it grabs unto soil and keeps it clamped together it prevents this makes the soil harder to wash away

Answer:

When the leftovers are left in the autumn, they have two purposes:

- Preventing erosion; the roots remain in the ground, so they hold it tightly till the next planting of the crops.

- Fertilizing the soil with natural material; the roots will not rot quickly in the colder period of the year, but will start rotting much faster in the spring, thus they will enrich the soil.

If someone were to be researching and studying similarities between our sun and a neighboring star, what kind of scientific investigation would they be conducting

Answers

Answer:

a

Explanation:

because there both in the solar system

There are billions of galaxies in the universe and each contains trillions of stars which are different in size, distance from the earth, brightness etc.When we scientifically investigate about this we can obtain the stars of similarity to sun in brightness and size.

What is galaxies?

Galaxies are a group of stars, dust and dark matter joined together by the force of gravitation. Three trillions of stars in each galaxies. Some stars forms a group of certain  size and shape and number also they are called constellations.

Sun is the closest star to earth. Thus sunlight is the major source of energy in earth. Sunlight reaches the earth surface within a time of 8 minute and 6 seconds.

The star which nearest to sun is named proximacentory which far from the earth and we can see it as spot of light in the sky. There are many more stars which are giants are more brighter than sun.

The brightness and luminosity is determined based on the distance from the earth. Which can be calculated in terms of light years. Each star has an age and length of life. After that the star may die still their light energy can be seen in sky because their light takes more years to reach here.

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the thermodynamic processes that occur in nature ____________.

Answers

Answer:

The thermodynamic processes that occur in nature convert thermal energy into mechanical energy.

The thermodynamic processes that occur in nature are according to the law of thermodynamics.

The thermodynamics processes seen in nature are guided by the law of thermodynamics. The role of energy and heat transmission in physical systems is guided by these laws.

The laws are:

(1) Energy cannot be created nor destroyed in a system, according to the first law of thermodynamics, Also, referred to as the law of energy conservation. Only from one form to another, the energy can be transmitted or altered. Energy is conserved through natural processes, keeping the overall amount constant.

(2) Second law of thermodynamics: states that the overall entropy of an isolated system tends to increase over time in any natural process. This suggests that processes progress towards a state of increasing disorder.

Hence, the thermodynamic processes are guided by the law of thermodynamics.

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What average force magnitude is required to stop a 15,000 kg train in 12.1 s if the train is traveling at 86 km/hr

Answers

Answer:

Explanation:

Givens

m = 15000 kg

t = 12.1 seconds

vi = 86 km / hr

vf =0

Formula

F = m*a

a = (vf - vi)/ t

vi has to be converted to m/s

86 km/hr [1000 m / 1 km] * [1 hour / 3600 seconds]

86 * 1000 / 3600 = 23.89 m/s

Solution

a = (vf - vi) / t

a = (0 - 23.89)/12.1

a = - 1.97 m/s^2 The minus means that the trains is slowing down.

F = 15000 kg * - 1.97 m/s^2

F = -29615.7 Newtons.

A camper stands in a valley between two parallel cliff walls. He claps his hands and notices that the echo from the nearby wall returns 0.9 s later while the echo from the farther wall returns 1.10 s later. If the air temperature is -10 C, how wide is the valley?

Answers

5,658 ft is your answer I believe

based on what you know about the location in relation to the sun why is this called the goldilock zone in other galaxies

Answers

Answer: It's an area that's an optimal distance from the sun for potentially supporting  life

This Constitutional right forbids Congress from sending a person to prison__
Explain what this Constitutional right is:___

Answers

The formation and operation of prisons, as well as inmates' rights, are governed by federal and state regulations. Although prisoners may not have full constitutional rights, the Eighth Amendment's restriction on cruel and unusual punishment protects them.

The best evidence for dark matter in the milky way comes from the observation that the rotation curve

Answers

It’s quite flat at great distance from the center

mars one mission essay

Answers

so bassicly Mars is a planet

Explanation:

planet

consider an air-filled balloon weighted so that it is on the verge of sinking. now, if you push it beneath the surface, it will

Answers

Given our understanding of physics, we can conclude that once the balloon is pushed under the surface, it will sink.

One key factor to take into account here is to remember that the density of a ballon can change when exposed to a higher pressure. This is due to the elastic nature of the material that makes up the ballon, and the nature of gas atoms that allow them to be compressed.

Therefore, when the balloon is pushed underwater, the surrounding water will squeeze the balloon, thus incrementing its density. Once the density of the balloon rises, this, in addition to the weight to which it is attached, will make it heavier than the water it is in, and the balloon will sink.

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test questions!!!!!!!!

Answers

Answer:

B. surface wave

Hãy giải thích sự phát âm của cái sáo khi thổi vào nó

Answers

Giải thích các bước giải:

Âm phát ra từ cái sáo khi thổi là do:

-Không khí ngoài ống sáo chuyển động và phát ra âm thanh.

-Thân sáo chuyển động và phát ra âm thanh.

-Thân sáo dao động và phát ra âm thanh.

-Cột không khí trong ống sáo dao động và phát ra âm thanh.

Arthur (mass 79 kg) and Violet (mass 50 kg) are trying to play on a seesaw. If Violet sits 4 m from the fulcrum, at what distance from the fulcrum should Arthur sit

Answers

Hi there!

There are two torques acting on the system:

τ (Arthur) = RW = R(790N)

τ (Violet) = RW = 4(500N) = 2000N

∑τ = 0 = τ(Violet) - τ(Arthur)

Thus:

τ(Violet) = τ(Arthur)

2000 = 790R

R ≈ 2.53m

An object has an acceleration of 12.0 m/s/s. If the NetForce was tripled and the mass was doubled, then the new acceleration would be _____ m/s/s

Answers

Answer: that would be New acceleration would be 12 m/s²

Explanation:

If you have a rocket that has a mass of 20kg and is accelerating at 25 m/s what force
would that rocket experience?
a . 20N
b . 40000N
c. 500N
d. 25N

Answers

F = ma
F = (20kg) x 25
= 500N
So your answer is C :)
Always remember “FAM” In the shape of a triangle … so F will be at the top and A&M at the bottom that way you will remember that F = mass x acceleration
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