Trình bày phương án xác định khối lượng riêng của một vật rắn không thấm nước (bỏ lọt vào bình chia độ) từ các dụng cụ sau: Một lò xo có móc treo; thước đo độ dài có độ chia thích hợp; nước;
bình chia độ; sợi dây mảnh, nhẹ; giá thí nghiệm và một vật nặng đã biết khối lượng

Aboxcar traveling at 12 m/s approaches a string of 5 identical boxcars sitting stationary on the track. the moving boxcar collides and links with the stationary cars and they all move off together along the track. what is the final speed of the cars immediately after the collision? (you may take the mass of each boxcar to be 18,537 kg.)

Aturntable a is built into a stage for use in a theatrical production. it is observed during a rehearsal that a trunk b starts to slide on the turntable 10 s after the turntable begins to rotate. knowing that the trunk undergoes a constant tangential acceleration of 0.31 m/s2, determine the coefficient of static friction between the trunk and the turntable.

The man of mass m1 and the woman of mass m2 are standing on opposite ends of the platform of mass m0 which moves with negligible friction and is initially at rest with s = 0. the man and woman begin to approach each other. derive an expression for the displacement s of the platform when the two meet in terms of the displacement x1 of the man relative to the platform.