Một vật có khối lượng m vào một lò xo có độ cứng k thì vật dao động với chu kì 0.2s . Nếu treo thêm gia trọng ∆m = 225g vào lò xo trên thì hệ vật và gia trọng dao động với chu kì 0.3s . Cho π bình phương =10. Lò xo đã cho có độ cứng là

the word that best describes martin luther king jr.'s tone in the video is dignified

martin luther king, jr. was a social activist and baptist minister who played a key role in the american civil rights movement from the mid-1950s until his assassination in 1968. the video shows his manner and attitude having or showing a composed or serious manner that is worthy of respect so dignified is the correct answer

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.