1. A physics professor demonstrates his new "antigravity
parachute" by exiting from a helicopter at an altitude of
1.50x103 m with zero initial velocity. For 8.00 s he falls
freely. Then he switches on the "parachute" and falls with a constant
upward acceleration of 15.0 m/s2 until his downward speed
reaches 5.00 m/s, whereupon he adjusts his controls to maintain that
speed until he reaches the ground. a) On a single graph, sketch his
acceleration and velocity as functions of time. b) What is his speed
at the end of the first 8.00 s? c) For how long does he maintain the
constant upward acceleration of 15.0 m/s2? d) How far does
he travel during the upward acceleration in part c? e) How many
second are required for the entire trip from the helicopter to the
ground? f) What is his average velocity for the entire trip?
2. A ball is thrown upward with an initial velocity of 20.0 m/s. a)
How long is the ball in the air? b) What is the greatest height
reached by the ball? c) When is the ball 15.0 m above the ground?
3. A train pulls away from a station with a constant acceleration of
0.400 m/s2. A passenger arrives at the track 6.00 s after
the end of the train has passed the very same point. What is the
slowest constant speed at which she can run and catch the train?
4. Vector A has a magnitude of 6.0 m and points 30.0o north of east. Vector B has a magnitude of 4.0 m and points 40.0o south of west. What is the resultant of adding these two vectors together?
5. Noobus is a death-defying squirrel with miraculous jumping
abilities. Running to the edge of a flat rooftop, she leaps
horizontally with a speed of 6.00 m/s. If she just clears the 3.00 m
gap between the houses and lands on the neighbor's roof, what is her
speed upon landing?
6. Carlos is on his trail bike, approaching a creek bed that is 7.00
m wide. A ramp with an incline of 10.0o has been built for
daring people who try to jump the creek. Carlos is traveling at his
bike's maximum speed, 40.0 km/h. a) Should Carlos attempt the jump or
emphatically hit the brakes? b) What is the minimum speed a bike must
have to make this jump? Assume equal elevations on either side of the
creek.
Answers
#1. -78.5 m/s, 4.9 s, -205 m, 209 s, -7.18 m/s
#2. 4.08 s, 20.4, m, .991s and 3.09 s
#3. 4.8 m/s
#4. 2.2 m, 10 degrees (11.3) N of E
#5. 7.75 m/s
#6. 4.29 m (No), 14.2 m/s