Newton's fundamental laws

  • Thread starter checkmarks
  • Start date
1. The problem statement, all variables and given/known data
A parachutist of mass 70kg, in free fall at 136 km/h, opens a parachute. if the chute creates a 895 N air resistance force and the parachutist is being pulled down by a force of gravity at 686 N
a) find hte acceleration of the parachutist
b) how far does she fall in 5.0 s?

2. Relevant equations
Fnet = ma, d = v1t + 1/2at^2

3. The attempt at a solution
First i determined part A and i got the answer 3.0 m/s^2 [up]. which is correct in the answer key.
then i used the equation d = v1t + 1/2at^2, converting 136 km/h to m/s
d = v1t + 1/2at^2
d = 37.7 m/s(5s) + 1/2(3 m/s^2)[(5s)^2]

and i got 226.4 m. the correct answer is 150m. i dont know what i did wrong. i then tried using the acceleration due to gravity, 9.81 m/s^2 because it is a freefall but the answer was still wrong.
please help!!
 

Doc Al

Mentor
44,656
989
The person's initial speed is downward, thus negative.
 

Want to reply to this thread?

"Newton's fundamental laws" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Top Threads

Top