At a given instant in time, a 3 kg rock is observed to be falling with an acceleration of 5.0 m/s2. What is the magnitude of the force of air resistance acting on the rock? (Use g = 10 m/s2.)
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2007-01-24 08:06:54 · 1 answers · asked by bibun 2 in Science & Mathematics ➔ Physics
The net force on the rock, in the downwards direction, is the force (F1) due to gravity less the force (F2) due to air resistance. According to Newton;s Laws of Motion, this net force equals the mass of the rock (3kg) multiplied by its acceleration (5 m/s2). hence we have:
F1 - F2 = 3 x 5 = 15 N
where I have used the fact that kg multiplied by m/s2 are Newtons (N). Now the gravitational force is just the mass (3kg) times the acceleration of gravity, which you say is 10 m/s2. Hence:
F1 = 3 x 10 = 30 N
By substituting for F1 in the first equation, and solving for F2, we get:
F2 = 30 - 15 = 15 N
Hence the force due to air resistance in this case is 15 N.
2007-01-24 08:15:26 · answer #1 · answered by Always Hopeful 6 · 0⤊ 0⤋