Messages 7:30 PM 29% Homework #1, PHY 2003 1) A car accelerates uniformly from 1
ID: 1772578 • Letter: M
Question
Messages 7:30 PM 29% Homework #1, PHY 2003 1) A car accelerates uniformly from 10 m/s to 20 m/s in 5 seconds. a) How far does it travel in this time? b) After it reaches the speed of 20 m/'s, how long does it take to stop the car over distance of 100 m? 2) A ball thrown downward from the top of a 40 m high building takes 2 seconds to hit the floor. Determine its initial and final speeds 3) A projectile is fired from ground at 37 degrees above horizontal at speed 50 m's a) Determine the position of the highest point and the time it takes to reach it b) Determine the position and time at which it strikes a wall 200m away 4) See Figure 4) A lemming accelerates uniformly starting from rest 2 m before jumping horizontally from the top of a 20 m high cliff. What is the minimum acceleration roquired so that the lemming can clear the rocks stretching out 4 m from the base of the cliff 5) A baby falls from the top of a 45 m building. What is the minimam speed that Spiderman must push off from the same building one second later in order to catch the bahy before she strikes the ground 6) A pilot flies a plane from A to B.400 miles due North of A. Ifa Westward wind of 20 mph is present, determine the direction the pilot needs to aim the plane relative to the air and the speed at which he needs to fly the plane in order to arrive at B in two hours Rocks wan War 1Explanation / Answer
1)
a)
vi=10m/s, vf= 20m/s, t=5.0s
a= v/ t =(vf-vi)/t = (20-10)5.0 = 2.0 m/s^2
b)
vi=20m/s, vf=0m/s, d= 100m
d=vi*t +1/2at^2
d=vi*t +1/2*[vf-vi]/t*t^2
d=vi*t +1/2*[vf-vi]*t
100 = 20*t+1/2*(0-20)*t
t=10s