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PolarNik [594]
3 years ago
5

Người ta ném một hòn bi theo phương ngang với vận tốc ban đầu là 15m/s và nó rơi xướng đất sau 4s. Bỏqua sức cản của không khí v

à lấy g=10 m/s2. Hỏi hòn bi được ném từđộcao nào và tầm xa của nó là bao nhiêu?
Physics
1 answer:
Juliette [100K]3 years ago
5 0

Answer:

h = 80m L = 60m

Explanation:

Độ cao Ng ta ném hòn bi là

t=\sqrt{\frac{2h}{9}} => 4^2 = \frac{2h}{10}

h= 80m

Tầm bay xa:

L= Vo . t = 15.4 = 60m

Chúc học tốt nghen

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Forces are balanced when net force on the object is zero or the sum of all force on the object is zero.

For book kept on a shelf, the weight of the book in down direction is balanced by the normal force on the book by the shelf. hence the book kept on a shelf is an example of balanced force.

In case of air rushing out of balloon , the balloon experience a net force by the air coming out of it.

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A person has legs of length L = 1.10 m. (a) If the maximum angle between the legs during walking is ϕ = 50o , what is the person
vampirchik [111]

Answer:

a). Maximum Length L=0.929m

b). T=0.83 Hz or 1.2s

c). Longer, the effortless waling T=2.1 Hz or t=0.475s

d). t=1.2s V=0.774 \frac{m}{s}

t=0.475s V=1.95 \frac{m}{s}

Explanation:

Length legs=L=1.1m

angle=50

the step that give the person forms a triangle whose two sides are known and the angle that forms between them, then using trigonometry as the image

Divide the original triangle in two and form a right triangle so the angle is 25 and the L is hypotenuse and the opposite is the step length

a).

sin(\alpha) =\frac{op}{h}

op=h*sin(\frac{\alpha }{2})\\ op=1.1m*sin(\frac{50}{2})\\op=0.464m

Length of the step

L=0.464m*2

L=0.928m

b).

period=T

T=\frac{1}{time}=\frac{1}{t}\\ T=\frac{1}{1.2s}\\T=0.83 s^{-1}\\ T=0.83Hz

c).

T1=2\pi *\sqrt{\frac{L}{g}} \\T1=2\pi *\sqrt{\frac{1.1m}{9.8\frac{m}{s^{2}}}}\\ T1=2.1 Hz

The period is the inverse of the time of the motion so, the T1 is faster that the T because

t=\frac{1}{T1}=t= \frac{1}{2.1}=0.47s

d).

The speed is the relation between the distance with time so:

Vt=\frac{0.928m}{1.2s} \\Vt=0.773 \frac{m}{s} \\Vt=\frac{0.928m}{0.475s} \\Vt=1.953 \frac{m}{s}

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