1.
	Incorrect 	If you drive west at 20 km/h for one hour, then drive east at 15 km/h for one hour, your net displacement will be

Your Answer:
	5 km east. 	

Correct Answer:
	5 km west.
  	Review Chapter 3 in Giancoli. The west velocity is greater than the east velocity.

2.
	Incorrect 	

A 200-lb force is pulling on an object, as shown. The sign of the x and y components of the force are


Your Answer:
	x (positive), y (positive). 	

Correct Answer:
	x (negative), y (positive).
  	Left is negative. Review Chapter 3 in Giancoli.

3.
	Incorrect 	

Three boys each pull with a 20-N force on the same object. The resultant force will be


Your Answer:
	zero. 	

Correct Answer:
	20 N to the left.
  	Review Chapter 3 in Giancoli.

4.
	Incorrect 	Consider a plane flying with groundspeed Vg and airspeed Va in a wind with speed V. Which of the following relationships is true?

Your Answer:
	Vg will always equal Va + V 	

Correct Answer:
	Vg can have any value between Va + V and Va - V
  	Review the Examples in Chapter 3 in Giancoli.

5.
	Incorrect 	Two vectors, R and S, are known:

If vector S is subtracted from vector R, the vector T = R - S is


Your Answer:
		

Correct Answer:
	
  	Review Chapter 3 in Giancoli.

6.
	Incorrect 	Two vectors, R and S, are known:

If vector R is subtracted from vector S, the vector T = S - R is


Your Answer:
		

Correct Answer:
	
  	Review Chapter 3 in Giancoli.

7.
	Correct 	Two vectors, R and S, are known:

If vector S is added to the vector R, then the vector T = R + S is


Your Answer:
	

8.
	Incorrect 	If the acceleration vector of a body is perpendicular to the velocity vector, which of the following must be true?

Your Answer:
	The speed is changing. 	

Correct Answer:
	The direction is changing.
  	This will never be true if the acceleration is perpendicular to the velocity. Review Chapter 3 in Giancoli.

9.
	Incorrect 	A vector of magnitude 10 has an angle with the positive x-axis (east) of 120 degrees. What are its components?

Your Answer:
	5 and 8.7 	

Correct Answer:
	-5 and 8.7
  	This would be true if the vector was in the first quadrant. Review Chapter 3 in Giancoli.

10.
	Incorrect 	A vector of magnitude 10 has an angle with the positive x-axis (east) of -60 degrees. What are its components?

Your Answer:
	5 and 8.7 	

Correct Answer:
	5 and -8.7
  	This would be true if the vector was in the first quadrant. Review Chapter 3 in Giancoli.

11.
	Incorrect 	A vector has components x = 6 m and y = 8 m. What is its magnitude and direction?

Your Answer:
	10 m and 30 degrees 	

Correct Answer:
	10 m and 53 degrees
  	Your magnitude is correct. Review Chapter 3 in Giancoli.

12.
	Incorrect 	A vector has components x = -2 m and y = -2 m. What is its direction (angle with respect to east)?

Your Answer:
	45 degrees 	

Correct Answer:
	225 degrees
  	This answer is in the first quadrant. Review Chapter 3 in Giancoli.

13.
	Incorrect 	Three vectors have components (x,y): A = (2,3), B = (4,-7) and C = (-6,-3). What is the magnitude of the resultant vector (D = A + B + C)?

Your Answer:
	-7 	

Correct Answer:
	7
  	The magnitude is always positive. Review Chapter 3 in Giancoli.

14.
	Correct 	Three vectors have components (x,y): A = (2,3), B = (4,-7) and C = (-6,-3). What is the magnitude of the resultant vector (D = A - B - C)?

Your Answer:
	13.6

15.
	Incorrect 	Suppose that several projectiles are fired on level ground. Which one will be in the air longest?

Your Answer:
	The one with the farthest range, R. 	

Correct Answer:
	The one with the highest maximum elevation, h.
  	Review the Examples in Chapter 3 in Giancoli.

16.
	Incorrect 	Which of the following does not affect the range of a projectile?

Your Answer:
	V0 Initial Speed 	

Correct Answer:
	x0 Initial Horizontal Position
  	Review the Examples in Chapter 3 in Giancoli.

17.
	Incorrect 	Which of the following must be zero for a projectile to achieve its maximum range?

Your Answer:
	Vxf 	

Correct Answer:
	yf
  	This is an easy mistake to make. The range is achieved just before the projectile hits the ground. Review the Examples in Chapter 3 in Giancoli.

18.
	Incorrect 	Which of the following must be zero for a projectile to be at its maximum height?

Your Answer:
	Vxf 	

Correct Answer:
	Vyf
  	Its elevation is independent of its horizontal motion. Review the Examples in Chapter 3 in Giancoli.

19.
	Incorrect 	You hit a handball too hard and it lands, moving horizontally, on top of a roof. If its original velocity was V0 at an angle θ above the horizontal, then the velocity it lands on the roof with is

Your Answer:
	zero 	

Correct Answer:
	V0cos θ
  	Good try, but still wrong. Projectile motion ends just before the projectile hits the ground. Review the Examples in Chapter 3 in Giancoli.

20.
	Incorrect 	You throw a pebble upward as shown, with a velocity V0 at an angle θ, from a roof (at point J) h ft above the ground. If the pebble rises upward to h ft above the roof (to point K), then falls to the ground below (to point L), its speed when it hits the ground is

Your Answer:
	V0. 	

Correct Answer:
	between V0 and 2V0.
  	This is the maximum speed it would have upon passing the roof on the way down. Review Chapter 3 in Giancoli.

21.
	Correct 	Taking "up" as positive at the highest point, the acceleration of a projectile is

Your Answer:
	-9.8 m/s2

22.
	Incorrect 	If the sum of two vectors equals zero, the magnitude of their difference is

Your Answer:
	equal to the magnitude of either one. 	

Correct Answer:
	equal to twice the magnitude of either one.
  	The sum is zero. Review Chapter 3 in Giancoli.

23.
	Correct 	A sailboat travelling with a speed of 4 knots heads directly up river against a 3 knot current. Its speed over ground is

Your Answer:
	1 knot.

24.
	Incorrect 	A sailboat travelling with a speed of 4 knots heads directly down river with a 3 knot current. Its speed over ground is

Your Answer:
	1 knot. 	

Correct Answer:
	7 knots.
  	Remember that they are in the same direction. Review Chapter 3 in Giancoli.

25.
	Incorrect 	A sailboat travelling with a speed of 4 knots heads directly across a river which has a 3 knot current. Its speed over ground is

Your Answer:
	1 knot. 	

Correct Answer:
	5 knots.
  	This would be true if the velocities were co-linear and opposed. Review Chapter 3 in Giancoli.