Người ta đúc một khối nhóm (A) và một khối sắt ( (Fe) hình khối với cũng khói lượng 5 kg Khối lượng riêng (2) của Al và Fe là 2 rho ki =2.7*10^ 3 kg/m^ 3 ; mu 4 =7,8*10^ 3; kg/m^ 3 Hỏi, khối vật liệu nào có kích thước lớn hơn? (a) khối nhằm (b) khối sắt (c) hai khối có cùng kích cỡ

Ablock of mass m = 2.5 kg is attached to a spring with spring constant k = 710 n/m. it is initially at rest on an inclined plane that is at an angle of θ = 23° with respect to the horizontal, and the coefficient of kinetic friction between the block and the plane is μk = 0.19. in the initial position, where the spring is compressed by a distance of d = 0.16 m, the mass is at its lowest position and the spring is compressed the maximum amount. take the initial gravitational energy of the block as zero. a) what is the block's initial mechanical energy? b) if the spring pushes the block up the incline, what distance, l, in meters will the block travel before coming to rest? the spring remains attached to both the block and the fixed wall throughout its motion.

Which is not a characteristic of a heat pump? a. it is used in air conditioners. b. it uses a refrigerant. c. it requires no work. d. it reverses the normal flow of thermal energy.

Which of the following is the phase that results when the moon is on the opposite side of the earth from the sun? a. quarter moon b. crescent moon c. new moon d. full moon