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sladkih [1.3K]
3 years ago
7

Câu 5. Một vật dao động điều hòa với phương trình x = 20cos(10pit +pi/2) (cm). Xác định thời điểm đầu tiên vật đi qua vị trí có

li độ x = 5 cm theo chiều âm kể từ thời điểm t = 0.
Physics
1 answer:
NARA [144]3 years ago
6 0

Answer:

Explanation:lớp 12 à

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A man pulls a sled at a constant velocity across a horizontal snow surface. if a force of 80 n is being applied to the sled rope
balandron [24]
A constant velocity implies the two forces must be equal and opposite.
Friction acts horizontal to the ground, therefore we must find the force applied to the sled rope that acts horizontal to the ground.
Do this by resolving:
Force = 80cos53
The force opposing this is equal, and so also = 80cos53 = 48 N (2 sig. fig.)
3 0
4 years ago
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An 80 kg skateboarder moving at 3 m/s pushes off with her back foot to move faster.
Dmitry [639]

Answer:

640 J

640 J

Explanation:

ΔKE = ½ mv² − ½ mu²

ΔKE = ½ m (v² − u²)

ΔKE = ½ (80 kg) ((5 m/s)² − (3 m/s)²)

ΔKE = 640 J

Work = ΔE

Work = 640 J

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3 years ago
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Which is not part of nuclear chemistry? A. Strong nuclear force B. Double-replacement reactions C. Radioactivity D. Nuclear deca
ziro4ka [17]

The correct choice is

B. Double-replacement reactions

in this type of reaction , two ionic compounds react and swaps their cations or anions giving two new compounds in the product. hence the double replacement reactions does not deal with the nucleus. all other terms like strong nuclear forces, radioactivity and nuclear decay deal with the nucleus.

8 0
4 years ago
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A 4.8-kg block attached to a spring executes simple harmonic motion on a frictionless horizontal surface. At time t=0 s, the blo
garri49 [273]

Answer:

E) 80 N/m

Explanation:

Given;

mass of the block, m = 4.8 kg

displacement of the block, x = -0.5 m

velocity of the block, v = -0.8 m/s

acceleration of the block, a = 8.3 m/s²

From Newton's second law of motion;

F = ma

Also, from Hook's law;

F = -Kx

where;

k is the force constant

Thus, ma = -kx

k = -ma/x

k = -(4.8 x 8.3) / (-0.5)

k = 79.7 N/m

k ≅ 80 N/m

Therefore, the force constant of the spring is closest to 80 N/m

4 0
3 years ago
Steam is leaving a 4-L pressure cooker whose operating pressure is 150 kPa. It is observed that the amount of liquid in the cook
Anna71 [15]

Answer:

The mass flow rate is 2.37*10^-4kg/s

The exit velocity is 34.3m/s

The total flow of energy is 0.583 KJ/KgThe rate at which energy leave the cooker is 0.638KW

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7 0
2 years ago
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