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1.two 2.changing 3.acceleration 4.zero 5. same
6.zero 7.negative 8.speed 9.zero 10.acceleration
The gravitational force interact between ………. .
(18) The weight of 50 kg mass is ……….. .
(19) The nuclear force is a ……. range force.
(20) The ratio of mass to volume is defined as ……… .
(21) The density of ice is ……….. than that of water.
(22) The symbol of density is ρ and it is a …….. quantity.
(23) The SI unit for pressure is …….. .