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BartSMP [9]
3 years ago
6

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:
Marrrta [24]3 years ago
5 0

Answer:

30.25 m/s

46.68 m

Explanation:

Work Energy theorem states that

W = ½mv2² - ½mv1²

W = ½m(v2² - v1²)

Net work done by the force = -mgd

Net work done = -m * 9.8 * 14.8

Net work done = -145m

Using the work energy theorem

-145m = ½m(v2² - v1²)

-145m = ½ * m(25² - v1²)

-290m = 625m - v1²m

v1² = 625 + 290

v1² = 915

v1 = √915 = 30.25 m/s

B

-mgd = ½m(v2² - v1²), where v2 = 0, so

-mgd = ½mv1²

Making d the subject of the formula, we have

d = -½mv1²/mg

d = v1²/2g

d = 915/ 2 * 9.8

d = 915 / 19.6

d = 46.68 m

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Read 2 more answers
A motorboat heads due east at 16 m/s across a river that flows due south at 9.0 m/s. a.) What is the resultant velocity of the b
alukav5142 [94]

Answer:

a)V=18.35 m/s (South -East)

b) t =7.41 m/s

c)D= 66.70 m

Explanation:

Given that

Velocity of boat in east direction = 16 m/s

Velocity of river = 9 m/s

a)The resultant velocity V

V=\sqrt{16^2+9^2}\ m/s

V=18.35 m/s (South -East)

b)

We know that

Distance = Velocity x time

Lets t time takes to cross the river

136 = 18.35 x t

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c)

   The distance covered downstream  

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D= 7.41 x 9 m

D= 66.70 m

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3 years ago
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