PHY 101 Mock Test 1

Newton’s second law for a system states that the net external force equals the total mass times the acceleration of the center of mass. Internal forces cancel in pairs.

This principle asserts that the fundamental laws of motion are invariant (take the same form) for all observers moving with constant velocity relative to each other.

This is the operational definition: a frame where an object with no net force acting on it moves with constant velocity (or remains at rest).

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.

W_net = ΔKE. This is a fundamental theorem derived from Newton’s second law, linking forces (via work) to changes in motion (via kinetic energy).

This is the definition of a perfectly elastic collision.

A world line on a space-time plot shows an object’s position (space) at every moment (time).

The center of mass of any system under the influence of a uniform gravitational field follows the simple parabolic trajectory of a point mass.

An event is a fundamental concept defined by its spatial coordinates (x, y, z) and its time coordinate (t).

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

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.

This is the Law of Conservation of Linear Momentum: If ΣF_ext = 0, then ΔP_total = 0.

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

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.

Just as mass resists linear acceleration (F=ma), the moment of inertia (I) resists angular acceleration (τ=Iα).

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

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.

Rotational KE = (1/2)Iω². KE is proportional to ω², so doubling ω increases KE by a factor of 2² = 4.

v_AB = v_A – v_B = (60 N) – (80 N) = -20 N, which is 20 km/h in the opposite direction (South).

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