I throw a piece of chalk up toward the ceiling. The piece of chal leaves my hand
ID: 1274253 • Letter: I
Question
I throw a piece of chalk up toward the ceiling. The piece of chal leaves my hand when its distance from the floor is 1meter. The ceiling is 3 meters from the floor. a. What is the minimal initial speed of the piece of chalk if i want it to touch the ceiling. B. How long will it take to go back to the floor. C. What will be the velocity of the piece of chalk when it reaches the floor?
An object moves with constant acceleration. At t=0 position is 0. At t=1 position is 1. At t=2 position is 5. A. what is its acceleration. B. What is its velocity at t=0. C. What is the average velocity in the first 1.5 seconds.
Explanation / Answer
1)a)Min speed is such that velocity at ceiling is 0
mgh=0.5mv^2
v=sqrt(2gh)=sqrt(2*9.8*2)=6.26m/s
b)-1=6.26*t-0.5*9.8*t^2
Solving for t, t=1.42s
c)v=sqrt(u^2+2gh')=sqrt(6.26^2+2*9.8*1)=7.67m/s
2) a)x(1)=1
1=u+0.5a
x(2)=5
5=2u+2a
Solving simultaneously,
a=3m/s^2
b)u=-0.5m/s
v(1.5)=-0.5+3*1.5=4m/s
Average velocity=(-0.5+4)/2=1.75m/s