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lord [1]
3 years ago
5

You throw a 20-N rock vertically into the air from ground level. You observe that when it is a height 14.8m above the ground, it

is traveling at a speed of 25.0 m/s upward.
A) Use the work-energy theorem to find its speed just as it left the ground. What is it?
B) Use the work-energy theorem to find its maximum height. What is it?
Physics
1 answer:
VladimirAG [237]3 years ago
4 0

Answer:

(A) The speed just as it left the ground is 30.25 m/s

(B) The maximum height of the rock is 46.69 m

Explanation:

Given;

weight of rock, w = mg  = 20 N

speed of the rock at 14.8 m, u = 25 m/s

(a) Apply work energy theorem to find its speed just as it left the ground

work = Δ kinetic energy

F x d = ¹/₂mv² - ¹/₂mu²

mg x d = ¹/₂m(v² - u²)

g x d = ¹/₂(v² - u²)

gd = ¹/₂(v² - u²)

2gd = v² - u²

v² = 2gd  + u²

v² = 2(9.8)(14.8) + (25)²

v² = 915.05

v = √915.05

v = 30.25 m/s

B) Use the work-energy theorem to find its maximum height

the initial velocity of the rock = 30.25 m/s

at maximum height, the final velocity = 0

- mg x H = ¹/₂mv² - ¹/₂mu²

- mg x H = ¹/₂m(0) - ¹/₂mu²

- mg x H = - ¹/₂mu²

2g x H = u²

H = u² / 2g

H = (30.25)² / 2(9.8)

H = 46.69 m

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creativ13 [48]

Answer: a) 456.66 s ; b) 564.3 m

Explanation: The time spend to cover any distance a constant velocity is given by:

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For the faster students t=780 m/1,9 m/s= 410.52 s

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In order to calculate the distance that faster student should  walk

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8 0
3 years ago
Consider 2 steel rods, A and B, B has three times the area and twice the length of A, so young modulus of B will be what factor
AVprozaik [17]

Answer:

  \frac{Y}{Y_o} = 2/3

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The yuong modulus of a rod is defined as the relationship between the tensile strength and the strain

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let's use the subscript "o" for rod A

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we substitute

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