Một vật dao động điều hòa theo phương trình x = 3cos(2πt - π/3), trong đó x tính bằng xentimét (cm) và t tính bằng giây (s). Hai thời điểm đầu tiên lúc vật có tốc độ cực đại là A. t1 = 1/12 (s), t2 =7/12 (s) B. t1 =5/12 (s), t2 =11/12 (s)
C. t1 =6/12 (s), t2 =2/3 (s) D. t1 =1/3 (s), t2 =11/12 (s)

There is a theory that indicates that dinosaurs became extinct when about 65 million years ago, a large asteroid hit the earth surface. dust caused by this collision blocked the sunlight reaching the earth's surface and many forms of life became extinct due to the cold. fearing this threat, how large the radius of an asteroid should you be looking for if the dangerous asteroid size is approximately the same as the one that killed the dinosaurs? available data suggests that about 18% of that asteroid's mass ended up as a dust spread evenly over earth after eventually settling out of the upper atmosphere. about 0.0180 g/cm^2 of dust, which is chemically different than the earth's rock, covered the earth's surface. typical asteroids have a density of about 1.9 g/cm^3. now that we know the size of the asteroid, how much energy was released during impact, assuming all of it was just the kinetic energy of the asteroid right before the impact?

Acricket ball of 70g moving with a velocity of 0.5 m/s is stopped by a player in 0.5s what is the force applied to stop the ball

What do elements in a family tend to share. a.) similar periods b.) similar groups c.) similar atomic symbols d.) similar chemical properties and characteristics