Một lò xo được treo thẳng đứng , đầu trên của lò xo được giữ chuyển động đầu dưới theo vật có khối lượng \(m=100g\), lò xo có độ cứng \(k=25\left(Nm\right)\). Kéo vật rời khỏi VCTB theo phương thẳng đứng hướng xuống một đoạn 2 cm , truyền cho nó là vận tốc \(10\sqrt{3n}>\left(\frac{cm}{s}\right)\)theo phương thẳng đứng lên . Chọn góc tg là lúc thả vật , góc toạ độ là VCTB , c hướng phương xuống .

a) Viết PTDĐ

b) Xác định điểm vật đi qua vị trí mà lò xo giãn cách 2 cm lần thứ nhất

Một chất điểm dao động điều hòa trên một đường thẳng quanh vị trí cân bằng O với chu kì \(T=0,314s\). Biết rằng khi \(t=0\)vật ở li độ \(x=-6cm\)với vận tốc bằng không.

a) Viết phương trình dao động. Tính giá trị vận tốc cực đại.

b) Tính vận tốc và gia tốc của chất điểm ở thời điểm \(t=\frac{\pi}{15}s\)và chiều chuyển động của nó.

c) Tính vận tốc khi \(x=3cm\)

có BN chữ Q

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Chiếu một chùm tia sáng trắng hẹp coi như một tia sáng vào một lăng kính có tiết diện thẳng là tam giác cân ABC, có góc chiết quang \(A=5^0\)theo phương vuông góc với mặt phẳng phân giác của góc chiết quang tại một điểm tới rất gần A. Biết \(n_t=1,54\)và \(n_đ=1,5\). Quang phổ hứng được trên một màn đặt song song và cách mặt phẳng phân giác của lăng kính là 2m. Tính bề rộng quang phổ thu được trên màn.