• Support PF! Buy your school textbooks, materials and every day products Here!

Finding maximum speed,

  • Thread starter Junkwisch
  • Start date
  • #1
31
0
In a 100 metre sprint, an athlete reaches her maximum speed in 3.0 seconds, starting from rest, assuming constant acceleration. She maintains her maximum speed until the finish, with an overall time of 11.0 seconds. Determine her maximum speed, vmax.


I'm trying to solve this problem but it is with little successes, I realised that this is not a constant motion (she stop accelerating). Thus I have to solve it with some kind of integration. Can any one tell me what equation do I have to use?
 

Answers and Replies

  • #2
adjacent
Gold Member
1,549
63
No, you don't need calculus here. Her acceleration was constant and she reached the maximum speed in 3 seconds and covered a distance of 100m.
You can use the kinematics equation involving final velocity, initial velocity, distance and time
 
  • #3
31
0
But I don't know what her acceleration is, even though it is constant for the first three seconds. Since I do not know her displacement in the last eight seconds.
 
  • #4
adjacent
Gold Member
1,549
63
But I don't know what her acceleration is, even though it is constant for the first three seconds. Since I do not know her displacement in the last eight seconds.
Oh, I think I misinterpreted the question. What you can do is draw a sketch of the velocity time graph. You don't know the velocity so leave the y-axis empty. Since the area under the graph is the distance , you can find the velocity.
It should be in a trapezium shape.
 
  • #5
31
0
Thankyou so much adjacent, it worked :D
 
  • #6
adjacent
Gold Member
1,549
63
You are welcome :smile:
 

Related Threads for: Finding maximum speed,

Replies
1
Views
694
  • Last Post
Replies
0
Views
2K
Replies
0
Views
3K
Replies
1
Views
811
Replies
1
Views
2K
Replies
11
Views
2K
Replies
1
Views
2K
Top