Name:    Ch 6 Motion in Two Dimension Test

True/False
Indicate whether the statement is true or false.

1.

The horizontal motion of a horizontally launched projectile affects its vertical motion.

2.

Projectile motion in two dimensions cannot be determined by breaking the problem into two connected one-dimensional problems.

3.

A fly riding on the blade of a fan spinning at a constant speed is not accelerating.

4.

The acceleration of an object in uniform circular motion always points toward the center of the circle.

5.

Centrifugal force is center-seeking acceleration.

6.

Centripetal acceleration is a scalar quantity.

7.

The relative velocity of object A to object C is the vector difference of object A’s velocity relative to object B, and object B’s velocity relative to object C.

Multiple Choice
Identify the choice that best completes the statement or answers the question.

8.

The path of a projectile through space is called its:
 a. equilibrant c. range b. torque d. trajectory

9.

A stone is thrown horizontally from the top of a 25.00-m cliff. The stone lands at a distance of 40.00 m from the edge of the cliff. What is the initial horizontal velocity of the stone?
 a. 2.260 m/s c. 17.70 m/s b. 15.60 m/s d. 22.05 m/s

10.

A ball is thrown horizontally from a hill 29.0 m high at a velocity of 4.00 m/s. Find the distance between the base of the hill and the point where the ball hits the ground.
 a. 2.43 m c. 10.06 m b. 9.73 m d. 3.28 m

11.

A sprinter runs at a speed of 3.00 m/s on a circular track that has a radius of 40.00 m. Find the centripetal acceleration of the sprinter.
 a. 0.225 m/s2 c. 0.750 m/s2 b. 4.44 m/s2 d. 0.0750 m/s2

12.

A 0.50-kg ball is attached to a string of 0.50 m and swung in a horizontal circle with a velocity of 1.0 m/s. Find the centripetal force of the ball.
 a. 0.50 N c. 2.0 N b. 1.0 N d. 2.5 N

13.

The path through space followed by a projectile is called the
 a. trajectory. c. thrust. b. transparency. d. acceleration due to gravity.

14.

Karl is at a carnival.  One of the midway games requires him to shoot at falling targets with an air rifle.  Where should Karl aim?
 a. He should aim below the falling target. b. He should aim above the falling target. c. He should aim directly at the target. d. He should aim at the ground below the target.

15.

To determine the y-component of a projectile’s velocity, what operation is performed on the angle of the launch?
 a. secant c. cosine b. tangent d. sine

16.

To determine the x-component of a projectile’s velocity, what operation is performed on the angle of the launch?
 a. secant c. cosine b. tangent d. sine

17.

The movement of an object at a constant speed around a circular radius is known as
 a. unified celestial movement. c. unilateral circus magic. b. uninformed circumstantial monotony. d. uniform circular motion.

18.

The centripetal force on an object in uniform circular motion is calculated using which formula?
 a. Fnet = mac c. Fnet = (vi2sin2q0)/g b. Fnet = 1/2acT2 d. Fnet = (4p2r)/T2

19.

Two toy dart guns are fired from the same height horizontally at the refrigerator.  One dart’s suction cup sticks to the refrigerator door, but the other dart falls short.  Explain why this may have happened.

20.

What is meant by the statement “the vertical and horizontal motions of a projectile are independent”?

21.

Some pilots are in training to make humanitarian aid deliveries for the U.N.  To help them get used to timing the release of their packages, they jog across the room at constant speed and drop tennis balls onto a Velcro mat with a target printed on it.  To hit the center of the target, when should the pilots drop the tennis balls, and why?

22.

If there is no such thing as centrifugal force, what causes you to slide to the outside of the seat when riding an amusement park ride that spins you in circles?

23.

Two people are riding a merry-go-round. One person is riding close to the inside edge of the platform, and the other is riding on the outside edge. The platform is 5 m wide, and the whole merry-go-round has a diameter of 20 m. The merry-go-round is making one rotation every 90 seconds.

In general terms, how does the acceleration of a person on a merry-go-round (or other rotating disc) vary with the radius of the disc?

24.

Brittany and Phillip are riding on a jet that is flying due south. Both of them are sitting in their seats. What is Brittany’s velocity relative to Phillip’s?

Problem

25.

A hiker throws a ball at an angle of 21.0° above the horizontal from a hill 21.0 m high. The hiker’s height is 1.750 m. The magnitudes of the horizontal and vertical components of the velocity are 14.004 m/s and 5.376 m/s, respectively. Find the distance between the base of the hill and the point where the ball hits the ground. (Consider the hiker’s height while calculating the answer.)

26.

Two grenades, A and B, are thrown horizontally with different speeds from the top of a cliff 70 m high. The speed of A is 2.50 m/s and the speed of B is 3.40 m/s. Both grenades remain in air for 3.77 s. Assume that the acceleration due to gravity is 9.86 m/s2. What is the distance between A and B if they are thrown along the same straight line?

27.

A boat traveling east covers a distance of 40.0 m in 20.0 s. It encounters a current moving at a speed of 2.50 m/s traveling north. Find the resultant velocity of the boat.

28.

A riverboat travels with a velocity of 4.60 m/s from one shore to another. The velocity of the river is 2.30 m/s. If the width of the river is 72.0 m, how far does the boat travel downstream to reach the other shore?

29.

An invading barbarian whirls a stone in a leather sling.  If the sling is 90 cm long, and the velocity of the stone is 90 m/s, what is the centripetal acceleration of the stone?

30.

A spider twirls a fruit fly around in a circle with radius 17.6 cm at the end of a web.  If the velocity of the fly is 110 cm/s, what is the centripetal acceleration of the fly?

31.

A spider twirls a fruit fly around in a circle at the end of a web.  If the web is 17.6 cm long, and the velocity of the fly is 110 cm/s, how much time does it take for the fly to make one complete revolution?

32.

An antelope moving at a speed of 16 m/s rounds a bend.  What is the radius of the tightest curve that the antelope can make if the centripetal acceleration does not exceed 20.0 m/s2?

33.

Josephine and Sunhee are playing shuffleboard on the deck of a cruise ship.  The ship is sailing due north at a speed of 3.0 m/s.  If Sunhee slides her puck along the deck, from east to west at 9.0 m/s, what is the velocity of the puck relative to the water?

34.

A grizzly bear wants to cross a river that is flowing south at 2.5 m/s.  If the bear is able to swim at a sustained speed of 3.0 m/s, at what angle should it swim if it wants to reach a point directly across the river from where it started (crossing west to east)?