mechanics (mass, force, acceleration, work, energy, momentum, velocity) - Category wise Question and Answer Practice Test with Solutions

Answer: (b)

A → (2) ; B → (4) ; C → (1)

The acceleration of mass 15 kg

a₃ = $[\text"15 - (6 + 4)"/\text"15 + 6 + 4"]$g = 2 m/s²

The acceleration of masses 4 kg and 6 kg with respect to pulley B is,

a = ${(6 – 4)}/{(6 + 4)}$ g = 2 m/s².

Answer: (b)

When a jet plane flies, it ejects gases in a backward direction at a very high velocity.

From Newton’s third law, these gases provide the momentum for the jet plane in the forward direction plus compensate for the force of gravity.

Answer: (c)

Answer: (a)

Answer: (c)

Uniform velocity:

Definition: The condition in which a body covers an equal level of distances in unequal intervals of time is called the uniform velocity. 

Examples of uniform velocity

When a particle moves with a uniform velocity, the slope of a displacement-time graph (Fig) is constant at all points.

It is a stable velocity, i.e., the velocity that does not change with time in scale or direction in space. This means that a body has this type of velocity if it travels at a constant speed along an instant line (i.e., in an exacting direction). There has been no change in either speed or direction.

The following are some examples:

• The Moon’s orbit around the Earth
• The movement of a watch’s hands
• Earth’s Rotation Earth’s Revolution
• Raindrops fall on the Earth’s surface. This is the velocity with which a body moves once it is started on a frictionless surface.
• All circular motion is an example: the movement of a fan and our clock hand.