PHY 101 Mock Test 1

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.

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

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

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.

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

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.

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

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).

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

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.

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.

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

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).

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.

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

θ = ω₀ t + (1/2)αt²
Explanation: This is the rotational kinematic equation, analogous to s = u t + (1/2) a t² in linear motion.

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

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.