# Motion in Two or Three Dimensions - Chapter No 4

Right Answers have been shown below in red color.

1. Velocity is defined as:

A. rate of change of position with timeB. position divided by timeC. rate of change of acceleration with timeD. a speeding up or slowing downE. change of position

2. Acceleration is defined as:

A. rate of change of position with timeB. speed divided by timeC. rate of change of velocity with timeD. a speeding up or slowing downE. change of velocity

3. Which of the following is a scalar quantity?

A. SpeedB. VelocityC. DisplacementD. AccelerationE. None of these

4. Which of the following is a vector quantity?

A. MassB. DensityC. SpeedD. TemperatureE. None of these

5. Which of the following is NOT an example of accelerated motion?

A. Vertical component of projectile motionB. Circular motion at constant speedC. A swinging pendulumD. Earth’s motion about sunE. Horizontal component of projectile motion

6. A particle goes from x = −2 m, y = 3 m, z = 1 m to x = 3 m, y = −1 m, z = 4 m. Its displacement is:

A. (1 m)i + (2 m)j + (5 m)kB. (5 m)i − (4 m)j + (3 m)kC. −(5 m)i + (4 m)j − (3m) kD. −(1 m)i − (2 m)j − (5m)kE. −(5 m)i − (2 m)j + (3m) k

7. A jet plane in straight horizontal flight passes over your head. When it is directly above you, the sound seems to come from a point behind the plane in a direction 30◦ from the vertical. The speed of the plane is:

A. the same as the speed of soundB. half the speed of soundC. three-fifths the speed of soundD. 0.866 times the speed of soundE. twice the speed of sound

8. A plane traveling north at 200 m/s turns and then travels south at 200 m/s. The change in its velocity is:

A. zeroB. 200 m/s northC. 200 m/s southD. 400 m/s northE. 400 m/s south

9. Two bodies are falling with negligible air resistance, side by side, above a horizontal plane. If one of the bodies is given an additional horizontal acceleration during its descent, it

A. strikes the plane at the same time as the other bodyB. strikes the plane earlier than the other bodyC. has the vertical component of its velocity alteredD. has the vertical component of its acceleration alteredE. follows a straight line path along the resultant acceleration vector

10. The velocity of a projectile equals its initial velocity added to:

A. a constant horizontal velocityB. a constant vertical velocityC. a constantly increasing horizontal velocityD. a constantly increasing downward velocityE. a constant velocity directed at the target

11. A stone thrown from the top of a tall building follows a path that is:

A. circularB. made of two straight line segmentsC. hyperbolicD. parabolicE. a straight line

12. Identical guns fire identical bullets horizontally at the same speed from the same height above level planes, one on the Earth and one on the Moon. Which of the following three statements

is/are true?

I. The horizontal distance traveled by the bullet is greater for the Moon.

II. The flight time is less for the bullet on the Earth.

III. The velocity of the bullets at impact are the same.

A. III onlyB. I and II onlyC. I and III onlyD. II and III onlyE. I, II, III

13. A stone is thrown horizontally and follows the path XYZ shown. The direction of the acceleration of the stone at point Y is:

A. ↓B. →C. ↑D. ←

14. A bullet shot horizontally from a gun:

A. strikes the ground much later than one dropped vertically from the same point at the sameinstantB. never strikes the groundC. strikes the ground at approximately the same time as one dropped vertically from the samepoint at the same instantD. travels in a straight lineE. strikes the ground much sooner than one dropped from the same point at the same instant

15. A bomber flying in level flight with constant velocity releases a bomb before it is over the target. Neglecting air resistance, which one of the following is NOT true?

A. The bomber is over the target when the bomb strikesB. The acceleration of the bomb is constantC. The horizontal velocity of the plane equals the vertical velocity of the bomb when it hitsthe targetD. The bomb travels in a curved pathE. The time of flight of the bomb is independent of the horizontal speed of the plane

16. The airplane shown is in level flight at an altitude of 0.50 km and a speed of 150 km/h. At what distance d should it release a heavy bomb to hit the target X? Take g = 10 m/s^{2.}

A. 150 mB. 295 mC. 420 mD. 2550 mE. 15, 000 m

17. An object is shot from the back of a railroad flatcar moving at 40 km/h on a straight horizontal road. The launcher is aimed upward, perpendicular to the bed of the flatcar. The object falls:

A. in front of the flatcarB. behind the flatcarC. on the flatcarD. either behind or in front of the flatcar, depending on the initial speed of the objectE. to the side of the flatcar

18. A ball is thrown horizontally from the top of a 20-m high hill. It strikes the ground at an angle

of 45◦. With what speed was it thrown?

A. 14 m/sB. 20 m/sC. 28 m/sD. 32 m/sE. 40 m/s

19. A stone is thrown outward from the top of a 59.4-m high cliff with an upward velocity component of 19.5 m/s. How long is stone in the air?

A. 4.00 sB. 5.00 sC. 6.00 sD. 7.00 sE. 8.00 s

20. A large cannon is fired from ground level over level ground at an angle of 30◦ above the horizontal. The muzzle speed is 980 m/s. Neglecting air resistance, the projectile will travel what horizontal distance before striking the ground?

A. 4.3 kmB. 8.5 kmC. 43 kmD. 85 kmE. 170 km