Question

Express each answer as a magnitude. (No negative answers)

A girl has a mass of 63 kg. What is her weight?

She jumps out of an airplane. What is her rate of acceleration at that moment?

She opens her parachute. This causes her to experience a drag force of 970 N, slowing her down. What is the net force acting on her at this moment?   What is her rate of acceleration at this moment?

As she slows, the drag force decreases to 810 N. What is her rate of acceleration at this moment?

As she continues to slow, the drag force decreases to the point that it is equal in strength to her weight. What is her rate of acceleration now?

She falls with a terminal speed of 3 m/s. How fast is she going as she lands on the ground?

Answer 1

mass of girl m = 63 kg;

(a) weight w = mg;

= 63 x 9.8;

= 617.4 N

(b) when she jumps out, her acceleration is due to the gravity i.e. 9.8 m/s².

(c) net force F = drag force - w;

= 970 - 617.4;

= 352.6 N

use newtons 2nd law;

F = ma;

352.6 = 63 x a;

a = 5.5968 m/s²

(d) now drag force changes to 810 N

so Fnet = 810 - 617.4;

=192.6 N;

192.6 = ma;

a = 192.6/63;

a = 3.057 m/s²

(e) Now drag force = weight of the girl;

Fnet = 0

therefore acceleration a = 0