## College Physics (7th Edition)

a). A hockey puck with weight of 0.5 lb is sliding freely across a section of very smooth horizontal ice. When the puck is sliding freely, there is no acceleration in the vertical direction. When the puck was at rest, there was zero acceleration in vertical direction. There is no change in the forces in vertical direction and thus (3) the upward force is the same in both situations is correct answer. b). Upward force is normal force which is equal to the weight of the puck. Mass=0.5lb=0.45kg. $F=m\times a=0.45\times 9.8=4.4N$
a). A hockey puck with weight of 0.5 lb is sliding freely across a section of very smooth horizontal ice. When the puck is sliding freely, there is no acceleration in the vertical direction. When the puck was at rest, there was zero acceleration in vertical direction. There is no change in the forces in vertical direction and thus (3) the upward force is the same in both situations is correct answer. b). Upward force is normal force which is equal to the weight of the puck. Mass=0.5lb=0.45kg. $F=m\times a=0.45\times 9.8=4.4N$