A puck slides across a horizontal ice sheet at constant speed

PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

1.5\,\text{kg}

puck slides across a horizontal ice sheet at constant speed. A

3.0\,\text{N}

force acts on the puck toward the +x direction, while an unknown horizontal force

F_x

due to air drag acts in the opposite direction. Which of the following must be true about

F_x

? (a)

F_x = 0

because no horizontal force is required once the puck is moving. (b)

F_x = 3.0\,\text{N}

directed toward the

-x

direction. (c)

F_x = 3.0\,\text{N}

directed toward the

+x

direction because forces follow the motion. (d)

F_x = 4.5\,\text{N}

directed toward the

-x

direction to overcome the puck’s inertia.