Tag: forces - vectors and moments

Quizzes (8) Questions (83)

Questions Related to forces - vectors and moments

Multiple choice physics motion of system of particles and rigid bodies centre of gravity turning effects of forces forces - vectors and moments

What is the position of centre of gravity of a cylinder?

  1. At the center of base circle

  2. At the center of top circle

  3. Cannot be determined

  4. At the mid point on the axis of cylinder
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Centre of gravity means a point from which the weight of a body or system may be considered to act. In uniform gravity it is the same as the centre of mass. For regular shaped bodies it lies at the centre of the that particular body. Hence for a cylinder centre of gravity lies at the midpoint of the axis of the cylinder.

Multiple choice physics motion of system of particles and rigid bodies centre of gravity turning effects of forces forces - vectors and moments

In an artificial satellite, the use of a pendulum watch is discarded, because :

  1. The satellite is in a constant state of motion

  2. The effective value of $g$ becomes zero in the artificial satellite

  3. The periodic time of the pendulum watch is reduced

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A pendulum watch relies on gravity to oscillate. Inside an orbiting satellite, objects are in a state of free fall, meaning the effective gravitational acceleration (g) is zero, causing the pendulum to stop oscillating.

Multiple choice physics motion of system of particles and rigid bodies centre of gravity turning effects of forces forces - vectors and moments

Given that there is a relationship between the orbital radius of a planet and its period of revolution and that the periods of revolution of Mercury, Earth, Jupiter and Neptune and nearly 0.24, 1, 11.8 and 165 years. It follows that the period of revolution of
1. Venus is less than 0.24 years
2. Mars is less than 12 years
3. Uranus is more than 165 years
4. Uranus is less than 165 years but more than 12 years.

  1. 1 and 3

  2. 4 only

  3. 3 o nly

  4. 2 and 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Kepler's third law states that the square of the orbital period is proportional to the cube of the semi-major axis (distance from the Sun). Therefore, planets further from the Sun have longer orbital periods. Mars (between Earth and Jupiter) must have a period between 1 and 11.8 years. Uranus (further than Neptune) would have a period longer than 165 years. The logic in option 2 and 4 fits the observed orbital distances.