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Harlamova29_29 [7]
3 years ago
13

Một chiếc thuyền có tốc độ 15 km / h trong nước tĩnh lặng đi 30 km về phía hạ lưu và trở lại trong tổng cộng 4 giờ 30 phút. Tốc

độ dòng chảy (theo km / h) là:
Physics
1 answer:
Ad libitum [116K]3 years ago
3 0
I don't know this answer
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A ceiling fan with 90-cm-diameter blades is turning at 64 rpm . Suppose the fan coasts to a stop 28 s after being turned off. Wh
mixas84 [53]

Answer:

the speed of the tip of a blade 10 s after the fan is turned off is 16.889 m/s.

Explanation:

Given;

diameter of the ceiling fan, d = 90 cm = 0.9 m

angular speed of the fan, ω = 64 rpm

time taken for the fan to stop, t = 28 s

The distance traveled by the ceiling fan when it comes to a stop is calculated as;

d = vt = \omega r\times  t= ( \frac{64 \ rev}{\min} \times \frac{2 \pi \ rad}{rev} \times \frac{1 \min}{60 \ s} \times 0.9 \ m) \times 28 \ s\\\\d = 168.89 \ m

The speed of the tip of a blade 10 s after the fan is turned off is calculated as;

v = \frac{d}{t} \\\\v = \frac{168.89}{10} \\\\v = 16.889 \ m/s

Therefore, the speed of the tip of a blade 10 s after the fan is turned off is 16.889 m/s.

4 0
3 years ago
A 30-gram bullet is fired and a 50-gram bullet is dropped simultaneously from the same height. Which will hit the ground first?
Marina86 [1]

Answer: the 30gram will hit the ground first

Explanation:the 30gram bullet will hit the ground first because it is fired

4 0
3 years ago
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Which among the following statement/s is correct?
seropon [69]

Answer:

(D) None

Explanation:

The force of gravity is the force pulling every element of matter together. The more the matter the higher the force of gravity.

Examples of this force at work are;

  • The force that causes an apple to fall from the tree
  • The force that causes a rock to roll downside a hill
  • The force causing people to walk on the earth surface instead of floating

The force that facilitates a pen on your hand to write on a paper is friction force between the pen and the paper. Gravitational force acts downwards thus force applied on an object beside you is not the force of gravity.

8 0
2 years ago
Why did you spin counterclockwise rather than clockwise
rodikova [14]
<span>Because of the orbit of the earth and the sun and the moon. </span>
6 0
3 years ago
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On Mars, the acceleration due to gravity is 3.77 m / s 2 . 3.77 m/s2. How far would a 15 g 15 g rock fall from rest in 2.5 s 2.5
Zinaida [17]

Answer:

s = 11.78 m

Explanation:

given,

acceleration due to gravity, g = 3.77 m/s²

mass of the rock = 15 g

time = 2.5 s

distance traveled = ?

using equation of motion

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

initial speed = 0 m/s

s = \dfrac{1}{2}at^2

s = \dfrac{1}{2}\times 3.77 \times 2.5^2

s = 11.78 m

distance traveled by the rock is equal to 11.78 m.

7 0
3 years ago
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