PHY 101 Mock Test 1

This is the definition of a perfectly elastic collision.

It is the mass-weighted average position of all particles in the system. It can lie outside a physical object (e.g., a doughnut).

A fundamental principle is that all terms in a valid physical equation must have the same dimensions. Dimensional analysis verifies this consistency but cannot determine dimensionless constants.

The ball has the train’s initial horizontal velocity relative to the ground. Under gravity alone, it follows projectile motion (a parabola) as seen by the ground observer.

A · B = |A||B|cosθ. For θ = 90°, cos90° = 0, so the dot product is zero.

Impulse, J = ∫ F dt (or F_avg Δt for constant force), is a measure of the change in momentum it produces.

By definition, the normal force is the component of contact force perpendicular (normal) to the surface. Its magnitude depends on the situation.

When vectors are opposite (180°), they subtract. The resultant magnitude is |A – B|, which is smaller than when they are at any other angle

Mechanical energy is lost to heat and sound (non-conservative forces). However, when considering all forms of energy, the total energy of the universe (ball + Earth + surroundings) is conserved.

The first law introduces the property of matter known as inertia, which is the tendency of an object to resist changes in its state of motion.

This is a key consequence of Einstein’s theory of special relativity. Simultaneity is not absolute but depends on the observer’s state of motion.

Multiplying by a negative scalar (-2) scales the magnitude by 2 and reverses the direction by 180 degrees.

With negligible external torque, L = Iω is constant. Decreasing I forces ω to increase to keep the product constant.

All points on a rigid rotating body share the same angular displacement, velocity, and acceleration. Linear quantities depend on radius (v = rω, a_c = rω²)..

It does not exchange matter or energy with its surroundings.
Explanation: An isolated system has no interactions across its boundary, no transfer of mass, heat, or work.

The law of conservation of momentum states that the total momentum of an isolated system remains constant. Mechanical energy is only conserved if non-conservative forces do no work.

Mechanical energy (KE+PE) is constant if the work done by all non-conservative forces (like friction) is zero.

With no horizontal force, the horizontal component of velocity remains unchanged. The vertical acceleration is always -g downward.

This is a common point of confusion. The two forces are an interaction pair between two different bodies, so they do not cancel for a single body.

For kinetic and maximum static friction, the force depends on the normal force and the coefficient of friction, not on the apparent area of contact.