What are the magnitude and direction of his acceleration?

Question

When a parachute opens, the air exerts a large drag force on it. This upward force is initially greater than the weight of the sky diver and, thus, slows him down. Suppose the weight of the sky diver is 956 N and the drag force has a magnitude of 1025 N. The mass of the sky diver is 97.6 kg. What are the magnitude and direction of his acceleration?

Answer 1

Using the y-axis as the path of motion, establish the conventions that any downward acceleration (i.e towards the earth) will have a positive sign, while movement away from the earth will have a negative sign.

Delta F = 956 N - 1025 N = - 69 N (the negative sign indicates that the initial net force will accelerate the skydiver upwards, away from the earth)

Magnitude of accel. = abs. value of Delta F/mass of skydiver

= 69 N/97.6 kg

~ 0.707 m/s^2