# Engineering Physics Questions and Answers – Motion in a Plane – 1

This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Motion in a Plane – 1”.

1. For motion in two or three dimensions, what is the angle between velocity and acceleration vectors?
a) 0°
b) 180°
c) Between 0° and 180°
d) 90°

Explanation: For motion in one dimension, the velocity and acceleration are always along the same line either in the same direction or in opposite direction. For motion in two or three dimensions, the angle between velocity and acceleration vectors may have any value between 0° and 180°.

2. A cyclist moves along a circular path of radius 70m. If he completes one round in 11s, calculate the total length of a path.
a) 40m
b) 440m
c) 0m
d) 11m

Explanation: Radius of the circular path, r = 70m
Time takes to complete one round, t = 11s
Total length of the path, s = 2πr = 2×22/7×70 = 440m.

3. An object thrown from an aeroplane is an example for ____________
a) Projectile motion
b) Resolution of forces
c) Composition of vectors

Explanation: A projectile is a name given to anybody which once thrown into space with some initial velocity, moves thereafter under the influence of gravity alone without being propelled by an engine or fuel. The path followed by a projectile is called its trajectory.

4. A ball is dropped downward from the roof of a building and simultaneously another ball is thrown in a horizontal direction, when will the balls reach the ground?
a) Same time and same place
b) The first ball will reach later than the second ball
c) The second ball will reach later than the second ball
d) Same time but different places

Explanation: Both the balls will reach the ground at the same time but at different places. The vertical motion is not affected by the horizontal motion. This is called the principle of physical independence.

5. A body is projected horizontally from the top of a cliff with a velocity of 9.8m/s. What time elapses before horizontal and vertical velocities become equal? Take g = 9.8m/s2
a) 9.8s
b) 0s
c) 10s
d) 1s

Explanation: Horizontal velocity at any instant, vx = u = 9.8m/s
Vertical velocity at any instant, vy = 0 + gt = 9.8t
9.8 = 9.8t
t = 1s.
Note: Join free Sanfoundry classes at Telegram or Youtube

6. Motion of the tip of second hand of the clock is an example for ___________
a) Uniform circular motion
b) Projectile motion
c) Motion in a plane with uniform velocity
d) Motion in a plane with constant acceleration

Explanation: If a particle moves along a circular path with a constant speed then its motion is said to be a uniform circular motion. Hence, the motion of the tip of the second hand of a clock is an example for uniform circular motion.

7. M0 L0 T(-1) is an example for ___________
a) Angular displacement
b) Angular velocity
c) Frequency
d) Time period

Explanation: The rate of change of angular displacement is called angular velocity. It is measured in radian per second and its dimensional formula is M0 L0 T(-1).

8. A circular motion is an accelerated motion.
a) True
b) False

Explanation: In a uniform circular motion, the direction of the velocity vector which acts along the tangent to the path, remains constant. So circular motion is an accelerated motion.

9. In projectile motion, magnitude remains constant but the direction continuously changes.
a) True
b) False

Explanation: In projectile motion, both magnitude and direction of acceleration remain constant, while in a uniform circular motion the magnitude remains constant but the direction continuously changes.

10. Calculate the angular speed of flywheel making 420 revolutions per minute.

Explanation: v = 420/60 revolution/ second
ω = 2πv = 2 × 22/7 × 420/60 = 44rad/sec.

11. Find the magnitude of the centripetal acceleration of a particle on the tip of a fan blade, 0.30 metre in diameter, rotation at 1200 rev/minute
a) 40 m/s2
b) 4737.6 m/s2
c) 245 m/s2
d) 20 m/s2

Explanation: v = 1200/60 = 20rps
ω = 2πv = 2×π×20 = 40π rad/sec
Magnitude of acceleration = rω2 = 0.30×(40π)2 = 4737.6 m/s2.

12. Pressure is a vector.
a) True
b) False

Explanation: Pressure is always taken to be normal to the plane of the area on which it is acting. As this direction is unique, it does not need any specification. So the pressure is not a vector.

13. What is the minimum number of coplanar vectors of different magnitudes which can give zero resultant?
a) One
b) Two
c) Three
d) Four

Explanation: If three vectors can be represented by the three sides of a triangle taken in the same order, then their resultant is a zero vector.

14. Two persons are pulling the ends of a string in such a way that the string is stretched horizontally. When a weight of 10kg is suspended in the middle of the string the string does not remain horizontal. Can the persons make it horizontal again by pulling it with a greater force?
a) Yes
b) No

Explanation: The persons cannot make it horizontal again by pulling it with a greater force because the vertical weight cannot be balanced by the horizontal force, however, large the two forces may be.

Sanfoundry Global Education & Learning Series – Engineering Physics.

To practice all areas of Engineering Physics, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]