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Q 01 / 25
A body can remain in uniform motion even when several forces act on it simultaneously.
Q 02 / 25
In an inertial frame, if the net external force on a particle is zero, its acceleration must be zero.
Q 03 / 25
Newton’s third law implies that the forces in an action–reaction pair always act on the same body.
Q 04 / 25
The frictional force on a body is always opposite to its velocity.
Q 05 / 25
Static friction can adjust its magnitude up to a certain maximum value.
Q 06 / 25
A car moving on a straight road with constant speed is in mechanical equilibrium.
Q 07 / 25
If a resultant force acts on a body, its speed must change.
Q 08 / 25
Tension in a light, inextensible string is the same at all points in one straight segment in equilibrium.
Q 09 / 25
Normal reaction exerted by a horizontal surface on a resting block is always equal to the weight of the block.
Q 10 / 25
In an action–reaction pair, forces are equal and opposite but may not balance each other in a free-body diagram.
Q 11 / 25
The coefficient of friction between two surfaces depends on the apparent area of contact.
Q 12 / 25
In uniform circular motion on a horizontal road, static friction provides the necessary centripetal force.
Q 13 / 25
The pseudo force on a mass \(m\) in a linearly accelerating frame of acceleration \(\vec{a}\) is \(-m\vec{a}\).
Q 14 / 25
Newton’s laws of motion hold exactly in any frame moving with constant velocity relative to the “fixed stars”.
Q 15 / 25
The kinetic friction on a sliding block always equals \(\mu_k N\), independent of its speed (within moderate speeds).
Q 16 / 25
In a system of two blocks connected by a light string on a smooth surface, internal tension forces can change the total linear momentum of the system.
Q 17 / 25
For a block in an accelerating lift, the apparent weight equals the normal reaction exerted by the floor on the block.
Q 18 / 25
During a collision of two isolated bodies in one dimension, the total momentum is conserved even if the collision is inelastic.
Q 19 / 25
A system moving under the action of only internal forces cannot have a changing centre-of-mass velocity.
Q 20 / 25
In a pulley system with a light, frictionless pulley and light string, the acceleration of all masses must be equal in magnitude.
Q 21 / 25
In a wedge–block system without friction, if the wedge is free to move on a smooth horizontal surface, the horizontal component of the normal between block and wedge is an internal force of the block–wedge system.
Q 22 / 25
For a bead constrained to move on a frictionless circular wire fixed in a car turning on a horizontal road, the normal reaction of the wire on the bead is the only real force responsible for changing the bead’s speed in the car’s frame.
Q 23 / 25
If the net external force on a system is always parallel to its velocity, the speed of the centre of mass must change but its direction of motion cannot change.
Q 24 / 25
In a rod of negligible mass pushing two unequal masses on a smooth surface, the internal forces on the rod at its two ends must be equal in magnitude.
Q 25 / 25
For any planar system of particles, if the vector sum of external forces is zero, then the system must be in static equilibrium.

Frequently Asked Questions

Newton's First Law states that a body remains at rest or in uniform straight-line motion unless acted upon by a net external force; this is called the law of inertia.

Newton's Second Law states that the rate of change of momentum of a body is proportional to the applied net force and takes place in the direction of the force, \(\vec{F} = \frac{d\vec{p}}{dt} = m\vec{a}\).

Newton's Third Law states that for every action there is an equal and opposite reaction; forces always occur in pairs acting on different bodies.

Inertia is the property of a body by virtue of which it resists any change in its state of rest or uniform motion in a straight line.

Linear momentum \(\vec{p}\) of a body is defined as the product of its mass and velocity, \(\vec{p} = m\vec{v}\).

Impulse of a force is the product of force and the time for which it acts and is equal to the change in momentum, \(I = F\Delta t = \Delta p\).

In an isolated system with no external force, the total linear momentum of the system remains constant during any interaction.

For constant mass, Newton's Second Law reduces to \(\vec{F}_{net} = m\vec{a}\).

An inertial frame is a reference frame in which Newton's First Law holds, i.e., a frame that is either at rest or moving with uniform velocity.

A non-inertial frame is a reference frame that is accelerating with respect to an inertial frame, in which fictitious or pseudo forces must be introduced to apply Newton's laws.

Pseudo force is an apparent force introduced in a non-inertial frame of reference, given by \(\vec{F}_{pseudo} = -m\vec{a}_{frame}\), acting opposite to the acceleration of the frame.

Normal reaction is the contact force exerted by a surface on a body, acting perpendicular to the surface.

Friction is the contact force that opposes the relative motion or the tendency of relative motion between two surfaces in contact.

Static friction acts between surfaces at rest relative to each other and can vary up to a limiting value, while kinetic friction acts when surfaces slide over each other with relative motion.

Limiting friction is the maximum value of static friction just before the body begins to move relative to the surface.
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