Câu 7. Một vật nhỏ khối lượng 250 gam được ném lên từ độ cao 8 m so với mặt đất theo phương thẳng đứng lên trên với tốc độ ban đầu 10 m/s. Bỏ qua sức cản của không
khí. Lấy g = 10m/s^.
a. Tính cơ năng của vật.
b. Tính độ cao cực đại.
c. Tính vận tốc của vật khi chạm đất.
d. Tính vận tốc và độ cao của vật khi động năng bằng 2 lần thế năng.

One day, after pulling down your window shade, you notice that sunlight is passing through a pinhole in the shade and making a small patch of light on the far wall. you see that the patch of light seems to be a circular diffraction pattern. it appears that the central maximum is about 1 cm across and you estimate that the distance from the window shade to the wall is about 3 m. what is (a) the average wavelength of sunlight? (b) the diameter of the pinhole?

Gordon is going for a run through the park, but it is cold outside. the low outside temperature could affect his personal safety.

Aperson gives a shopping cart an initial push along a horizontal floor to get it moving, and then lets go. the cart travels forward along the floor, gradually slowing as it moves. consider the horizontal force(s) on the cart while it is moving forward and slowing. which of the following statements is correct? (a) both a forward and a backward force are acting on the cart, but the forward force is larger. (b) only a forward force is acting which diminishes with time. (c) both a forward and a backward force are acting on the cart, but the backward force is larger. (d) only a backward force is acting, no forward force.