Physics 011

Chapter 3: Kinematics in Two Dimensions; Vectors
Practice Questions

PQ#3

 1

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

5 km east.

35 km west.

35 km east.

5 km west.

 2

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

x (positive), y (positive).

x (positive), y (negative).

x (negative), y (positive).

x (negative), y (negative).

 3

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

zero.

20 N to the left.

20 N up.

20 N down.

 4

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

Vg will always equal Va + V

Vg can be greater than Va + V

Vg can be less than Va - V

Vg can have any value between Va + V and Va - V

 5

Two vectors, R and S, are known:

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

 6

Two vectors, R and S, are known:

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

 7

Two vectors, R and S, are known:

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

 8

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

The speed is changing.

The direction is changing.

Both the speed and the direction are changing.

The direction is not changing.

 9

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

5 and 8.7

-5 and 8.7

5 and -8.7

-5 and -8.7

 10

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

5 and 8.7

-5 and 8.7

5 and -8.7

-5 and -8.7

 11

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

10 m and 30 degrees

14 m and 37 degrees

10 m and 53 degrees

14 m and 53 degrees

 12

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

45 degrees

135 degrees

225 degrees

-45 degrees

 13

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)?

-7

17.7

15

7

 14

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)?

13.6

15

52

7

 15

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

The one with the farthest range, R.

The one with the highest maximum elevation, h.

The one with the greatest initial velocity.

 16

Which of the following does not affect the range of a projectile?

vo Initial Speed

thetao Launch Angle

yo Initial Height

xo Initial Horizontal Position

 17

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

vxf

vyf

xf

yf

 18

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

vxf

vyf

yf

xf

 19

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

zero

vo sin q

vo cos q

2vo

 20

You throw a pebble upward as shown, with a velocity vo at an angle theta, 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

vo.

between vo and 2vo.

2vo.

greater than 2vo.

 21

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

-9.8 m/s^2

0 m/s^2

+9.8 m/s^2

 22

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

equal to the magnitude of either one.

equal to twice the magnitude of either one.

less than twice the magnitude of either one.

 23

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

1 knot.

7 knots.

3 knots.

5 knots.

 24

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

1 knot.

3 knots.

5 knots.

7 knots.

 25

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

1 knot.

3 knots.

5 knots.

7 knots.