Newtonian Mechanics and Forces

Once the wrench is thrown in space, it will continue moving indefinitely without any additional force needed. This is Newton's first law of motion in action - in the vacuum of space with negligible forces acting on it, the wrench will maintain its velocity without requiring force to 'keep it going'. The force was only needed to throw it initially, not to maintain its motion.

Newton's first law (law of inertia) states that objects resist changes in motion - a resting object stays at rest, and a moving object continues with constant velocity unless acted upon by an unbalanced external force. Options A, B, and C correctly describe this principle. Option D is false because a body CAN move at constant speed with an external force if the force is perpendicular to motion (like circular motion), or if balanced forces act on it.

When a body rests on a horizontal surface without external forces, two forces act on it: its weight (downward) and the normal reaction force (upward) from the surface. Since the question specifically asks about forces from the ground/surface, 'normal reaction' (B) is the correct answer. Friction only acts when there's motion or tendency to move.

This statement accurately describes subduction, which occurs at convergent plate boundaries. When a dense oceanic plate converges with a less dense continental plate, the oceanic plate is forced beneath the continental plate and into the mantle. This process creates deep ocean trenches, volcanic arcs, and can cause powerful earthquakes. The subducting plate melts as it descends, creating magma that rises to form volcanoes.

Fluid friction (drag force) is directly proportional to relative velocity at low speeds (Stokes' law: F = 6πηrv) and proportional to the square of velocity at higher speeds (F = ½ρv²CdA). It is never inversely proportional to speed - as speed increases, drag force always increases, not decreases. Therefore, the statement is false.

Rolling friction is significantly less than sliding friction because rolling involves less surface contact area between surfaces. When an object rolls, only a small portion of its surface touches the ground at any instant, reducing friction. Converting from sliding to rolling (like using ball bearings or wheels) is a fundamental principle in mechanical design to reduce energy loss and improve efficiency.

Frictional force is the odd one out because it is a contact force that requires physical contact between surfaces, whereas gravitational, electrostatic, and nuclear forces are fundamental non-contact forces that act at a distance. The other three are fundamental forces of nature, while friction is a derived force.

Newton's three laws of motion describe the relationship between forces and motion (1st: inertia, 2nd: F=ma, 3rd: action-reaction). Newton's law of universal gravitation is a separate theory about gravitational attraction between masses, not part of the three laws of motion.

Newton's first law states that an object remains at rest or in uniform motion unless acted upon by an external force. The question incorrectly phrases it as 'force, inertia must act' - inertia is the property that resists change in motion, not something that acts. The correct concept is that force causes change in motion.

In curved races (200m and 400m), runners experience centrifugal force which pushes them outward. Middle and outer lanes have less centrifugal force effect compared to inner lanes, making them preferred for maintaining better balance and speed through curves.

The newton, the SI unit of force, is named after Isaac Newton, the English physicist and mathematician who formulated the laws of motion and universal gravitation. His work laid the foundation for classical mechanics.

Newton's first law states that an object at rest stays at rest AND an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. A moving body with no net force will continue moving at constant velocity, not come to rest.

Friction is a non-conservative force because the work done against friction depends on the path taken - a longer path means more work is lost to friction. In contrast, conservative forces like gravity and electric force have work done that is independent of the path, depending only on initial and final positions.

Nuclear force (strong nuclear force) operates only at extremely short ranges within the atomic nucleus, about 1-3 femtometers. In contrast, electrostatic, magnetic, and gravitational forces are all long-range forces that can act over infinite distances, with their strength decreasing according to the inverse square law.