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Bess [88]
2 years ago
12

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
Physics
1 answer:
lys-0071 [83]2 years ago
6 0

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

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3 0
2 years ago
True or False<br><br> An object will slow down and stop as long as no forces act upon it
My name is Ann [436]

Answer:

false

Explanation:

Understand Newton’s first law of motion. Experience suggests that an object at rest will remain at rest if left alone, and that an object in motion tends to slow down and stop unless some effort is made to keep it moving. An object will go on forever if there were no forces to act upon it. In space, a rocket will go forever at the speed it projects.

5 0
3 years ago
Read 2 more answers
5 x 10 to the power electron cross through the cross section of a wire per second. What is the magnitude of electric current pas
Rom4ik [11]

. She replaces a straight electrical

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3 years ago
You are rushing to the train station to catch your morning commute. The train leaves the train station from rest with an acceler
Vanyuwa [196]

Answer:

a) t= 4.81 s,and t= 23.51.

b)d=6.88 m

c)v=4.8 m/s

Explanation:

Acceleration of train ,a= 0.6 m/s²

u = 0 m/s

Your speed ,V= 8.5 m/s

Lets take after t time he you catch the train

Distance travel by train in t time

d=ut+\dfrac{1}{2}at^2

d=\dfrac{1}{2}\times 0.6\times t^2  ----------1

d= V ( t- 4)

d= 8.5 ( t- 4)  --------2

By equating equation 1 and 2

0.3 t² =  8.5 ( t- 4)

0.3 t² -8.5 t + 34 = 0

t= 4.81 s and t= 23.51

It means that you will catch train after t= 4.81 s,and t= 23.51.

t=23.51 sec means that you will catch the train after 23.51 sec also because acceleration of train is low.

Distance travel

d= 8.5 ( t- 4)

t= 4.81 s

d= 8.5 ( 4.81- 4)  m

d=6.88 m

Lets speed = v

0.3 t² =  v ( t- 4)

0.3 t² - v t + 4 v = 0

To have one solution

D=\sqrt{b^2-4ac}

D= 0 Should be zero.

v²- 4 x 0.3 x 4 v

v = 4 x 0.3 x 4

v=4.8 m/s

6 0
3 years ago
On a cosmic calendar, in which the history of the universe is compressed into one year, how long is the average human life span?
netineya [11]

Answer:

If one were to use 5 billion years as the age of the universe and 75 years as the average human life span then

T = 75 / 5 E9 = 1.5E-8

The number of seconds in a year is 3600 * 24 * 365 = 3.2E7

If t = N * T   seconds in a year * fraction of human life span

t = 1.5E-8 * 3.2E7 = .48

A human life span is about 1/2 second compared to the life of the universe if the universe were compressed to a single year

8 0
2 years ago
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