Physics Contest Question 4

Sorry for the delay, the end of Ramadan had me super busy!
This is the FOURTH problem of the competition discussed in this thread. Please read the rules there for details on scoring and the prize.


  • Do NOT post your answers or work in this thread, please PM me your answer and work. You will receive TWO chances to answer correctly.
  • Within the PM include: Your name, status as a high schooler or recent graduate (yes/no), and whether you had any help answering the question.
  • Websites, textbooks, other people, physics professors/teachers, etc. are NOT allowed as resources! You are free to use these resources and submit an answer to see if you were correct (learning new concepts is great!), but you will be disqualified from earning points for any questions you do this for.

Problem 4:

A young man knows that his sister, a 50kg girl, is planning to run at constant speed of 4m/s and then dive onto an, initially at rest, 5kg sled on top of a snow covered (frictionless) 7m tall hill. He is considering jumping onto her sled when she has traveled a vertical displacement of 5 meters, but is unsure of how fast her sled will be moving at that point.

A: How fast will his sister be moving at the instant that she has traveled a vertical displacement of 5 meters?

B:Considering her speed at the instant discussed in part A, is it reasonable for her brother to try and jump onto her sled? Explain your reasoning.

Responses are due by MIDNIGHT (eastern!) this Thursday!