Physics 71 - Problem Set #1: Chapter 1 and 2
General Directions: Solve each problem carefully on a yellow paper. Write your COMPLETE
solution. No solution. No credit even if your answer is correct. Box your final answers.
1. Three horizontal ropes pull on a large stone stuck in
the ground, producing the vector forces A, B and C
shown in the figure.
(a) Find the fourth force that will bring the system in
equilibrium. Write it in component form and give its
magnitude and direction.
(b) Draw the fourth vector.
2. Answer the following questions for each of the graphs in the figure.
Question
Plot 1
Plot 2
(a) At what points are the acceleration of
the objects positive?
(b) At what points are the acceleration of
the objects negative?
(c) At what points are the acceleration of
the objects zero?
(d) At what points are the instantaneous
velocities zero?
3. A car making a 100.-km journey travels 40.0 km/h for the first 50.0 km. How fast must it
go during the second 50.0 km to average 50.0 km/h?
4. A bus accelerates at 1.50 m/s2 from rest for 12.0 s. It then travels at constant speed for
25 s, after which it slows to a stop with an acceleration of ­1.50 m/s2.
(a) How far did the bus travel?
(b) What was its average velocity?
5. At t=0, a stone is dropped from a cliff above a lake; 1.60 s later another stone is thrown
downward from the same point with an initial speed of 32.0 m/s. Both stones hit the
water at the same instant. Find the height of the cliff.
6. A falling stone takes 0.280 s to travel past a window 2.20 m tall. From what height above
the top of the window did the stone fall?