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ryzh [129]
3 years ago
15

A boy is playing with a ball of mass 72g attached to a string. He is moving it at constant speed in a horizontal circle of radiu

s 0.9m. a. State the net work done on the ball in one complete revolution. (1) b. The tension in the string is 60N. Determine the angular velocity of the ball. (4) c. Calculate the time it takes for the ball to complete 20 revolutions. (2)
Physics
1 answer:
irina [24]3 years ago
3 0

Answer:

Explanation:

radius of circle r = 0.9 m.

(a ) In a motion on circular path , work done is zero because force ( centripetal force ) acts perpendicular to displacement .

( b )

Tension in string T = m ω²r

Putting the values

60 = .072 x ω² x 0.9

ω² = 926

ω = 30.4 rad /s

angle made in 20 revolutions θ = 20 x 2π = 126.6 rad

time taken = θ / ω

= 126.6 / 30.4

= 4.16 s .

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the thermometer has its stem marked in millimeter instead of degree Celsius. the lower fixed point is 30mm and the upper fixed p
Lorico [155]

10°c

Explanation:

Given parameter;

Lower fixed point = 30mm

Upper fixed point = 180mm

Reading = 45mm

Unknown:

The degree celcuis temperature at 45mm = ?

Solution:

To solve this problem we simply compare the mm- scale to the celcius - scale that we know.

The upper fixed point is the boiling point of water

Lower fixed point is the freezing point of water

This shows that both the upper and lower fixed point of both thermometers are the same;

         mm-scale          °c scale

          180mm               100°c

            45mm                x

          30mm                  0°c

Solving;

                     \frac{x - 0}{100 -0} =  \frac{45 - 30 }{180- 30}

   x (150) = 100  x 15

   x = 10°c

learn more:

Temperature scales brainly.com/question/1603430

#learnwithBrainly

 

7 0
3 years ago
What is one of Kepler's laws of planetary motion?
iragen [17]

Answer:

a. Planets move on elliptical orbits with the Sun at one focus.

Explanation:

Johannes Kepler was an astronomer who discovered that planets had elliptical orbits in the early 1600s (between 1609 and 1619).

The three (3) laws published by Kepler include;

I. The first law of planetary motion by Kepler states that, all the planets move in elliptical orbits around the Sun at a focus.

II. According to Kepler's second law of planetary motion, the speed of a planet is greatest when it is closest to the Sun.

Thus, the nearer (closer) a planet is to the Sun, the stronger would be the gravitational pull of the sun on the planet and consequently, the faster is the speed of the planet in terms motion.

III. The square of any planetary body's orbital period (P) is directly proportional to the cube of its orbit's semi-major axis.

Hence, one of Kepler's laws of planetary motion states that planets move on elliptical orbits with the Sun at one focus. This is his first law of planetary motion.

4 0
3 years ago
In physics, for a given object, work divided by distance will equal
Genrish500 [490]
It is force because work/distance= force
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How does hydroelectric energy work
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<span>The water is held behind a dam, forming reservoir. The force of the water being released from the reservoir through the dam spins the blades of a giant turbine.</span>
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The force of gravitation between two spherical bodies is Gm1 m2 /r2, where r is separation between their dash
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Explanation:

F = Gm1m2/r^2

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