Page 62 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 4] MOTION IN A VERTICAL PLANE 47

4.11. A ball is thrown 40 below the horizontal at 4.0 m/s. After 0.50 s the horizontal component of the ball’s velocity
◦
will be
(a) 2.6 m/s (c) 3.4 m/s
(b) 3.1 m/s (d) 5.5 m/s

4.12. After 0.50 s the vertical component of the velocity of the ball of Question 4.11 will be
(a) 2.6 m/s (c) 4.9 m/s
(b) 3.1 m/s (d) 7.5 m/s

Supplementary Problems

4.1. A hunter aims a rifle directly at a squirrel on a branch of a tree. The squirrel sees the flash of the rifle’s firing. Should
the squirrel stay where it is or drop from the branch in free fall the moment the rifle is fired?

4.2. A stone is dropped from the edge of a cliff. (a) What is its velocity in meters per second 3 s later? (b) How far does it
fall in this time? (c) How far will it fall in the next second?

4.3. A girl throws a ball 20 m vertically into the air. (a) How long does she have to wait to catch it on the way down?
(b) What was its initial velocity? (c) What will be its final velocity?

4.4. The Sears Tower in Chicago is 1454 ft high. (a) How long would it take an object dropped from the top of the building
to reach the ground? (b) What would the object’s final velocity be?

4.5. A body in free fall reaches the ground in 5 s. (a) From what height in meters was it dropped? (b) What is its final
velocity? (c) How far did it fall in the last second of its descent?

2
4.6. The acceleration of gravity on the surface of Mars is 3.7 m/s . If a ball is thrown vertically downward at 10 m/s from
a cliff on Mars, (a) What will its speed be after 1 s? (b) After 3 s?
4.7. A ball is thrown vertically upward with a velocity of 12 m/s. (a) At what height is the ball 1 s later? (b) 2 s later?
(c) What is the maximum height the ball reaches?
4.8. A ball is thrown horizontally with a velocity of 12 m/s. (a) How far has the ball fallen 1 s later? (b) 2 s later?

4.9. A ball is thrown vertically downward with a velocity of 12 m/s. (a) How far has the ball fallen 1 s later? (b) 2 s later?

4.10. A pear is thrown vertically downward from a cliff 48 m high and reaches the foot of the cliff 2 s later. Find the initial
velocity of the pear.

4.11. A rifle with a muzzle velocity of 200 m/s is fired with its barrel horizontally at a height of 1.5 m above the ground. (a)
How long is the bullet in the air? (b) How far away from the rifle does the bullet strike the ground? (c) If the muzzle
velocity were 150 m/s, would there be any difference in these answers?
4.12. A ball is rolled off the edge of a table 3 ft high with a horizontal velocity of 4 ft/s. With what velocity does it strike
the floor?

4.13. A rescue line is to be thrown horizontally from the upper deck of a ship 30 m above sea level to a lifeboat 30 m away.
What should the velocity of the line be?

4.14. If the initial velocity of a projectile were doubled, how would its maximum range be affected?
4.15. A crossbow can shoot an arrow 100 m vertically upward. (a) What is its maximum horizontal range? (b) With what
velocity will the arrow strike the ground when shot vertically upward and when shot so as to have the maximum range?