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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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A 3.91 kg cart is moving at 5.7 m/s when it collides with a 4 kg cart which was at rest. They collide and stick together.
Nesterboy [21]

Answer:

<em>The velocity after the collision is 2.82 m/s</em>

Explanation:

<u>Law Of Conservation Of Linear Momentum </u>

It states the total momentum of a system of bodies is conserved unless an external force is applied to it. The formula for the momentum of a body with mass m and speed v is  

P=mv.  

If we have a system of two bodies, then the total momentum is the sum of the individual momentums:

P=m_1v_1+m_2v_2

If a collision occurs and the velocities change to v', the final momentum is:

P'=m_1v'_1+m_2v'_2

Since the total momentum is conserved, then:

P = P'

Or, equivalently:

m_1v_1+m_2v_2=m_1v'_1+m_2v'_2

If both masses stick together after the collision at a common speed v', then:

m_1v_1+m_2v_2=(m_1+m_2)v'

The common velocity after this situation is:

\displaystyle v'=\frac{m_1v_1+m_2v_2}{m_1+m_2}

There is an m1=3.91 kg car moving at v1=5.7 m/s that collides with an m2=4 kg cart that was at rest v2=0.

After the collision, both cars stick together. Let's compute the common speed after that:

\displaystyle v'=\frac{3.91*5.7+4*0}{3.91+4}

\displaystyle v'=\frac{22.287}{7.91}

\boxed{v' = 2.82\ m/s}

The velocity after the collision is 2.82 m/s

6 0
2 years ago
A conical container of radius 6 ft and height 18 ft is filled to a height of 11 ft of a liquid weighing 64.4 lb divided by ft cu
prisoha [69]

Answer:

Hello there, please see explanations for step by step answer.

Explanation:

Radius 6 ft and

Height 18 ft is filled to a height of 11 ft of a liquid weighing 64.4 lb divided by ft cubedlb/ft3.

How much work will it take to pump the contents to the​ rim.

See attached documents for clear solvings and further step by step explanations

4 0
2 years ago
I’ll give u BRAINLIEST PLEASE!! HURRY
zalisa [80]

Answer:

C

Explanation:

6 0
2 years ago
If your mass is 20kg, and you stand on the scale (witch is your force), and the acceleration due to gravity is10m/s^2, what does
Phantasy [73]
Weight = (mass) x (gravity)

= 200 Newtons.

(About 44 pounds. You're very skinny.)
5 0
3 years ago
Read 2 more answers
HELP PLEASE 20 POINTS SHOW WORK, ALL EQUATIONS
nataly862011 [7]

Answer:

s = 3 m

Explanation:

Let t be the time the accelerating car starts.

Let's assume the vehicles are point masses so that "passing" takes no time.

the position of the constant velocity and accelerating vehicles are

s = vt = 40(t + 2)  cm

s = ½at² = ½(20)(t)² cm

they pass when their distance is the same

½(20)(t)² = 40(t + 2)

10t² = 40t + 80

0 = 10t² - 40t - 80

0 = t² - 4t - 8

t = (4±√(4² - 4(1)(-8))) / 2(1)

t = (4± 6.928) / 2  ignore the negative time as it has not occurred yet.

t = 5.464 s

s = 40(5.464 + 2) = 298.564 cm

300 cm when rounded to the single significant digit of the question numerals.

7 0
2 years ago
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