Classical Mechanics - Newtonian Laws & Energy Conservation Flashcards

Question 1

What are the SI units for power?

Accepted Answer

The SI unit for power is the Watt (W), which is equivalent to Joules per second ($J/s$).

Question 2

What is Newton's First Law of Motion?

Accepted Answer

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. This is also known as the Law of Inertia.

Question 3

Provide an example of Newton's First Law.

Accepted Answer

A book resting on a table will remain at rest unless pushed or pulled. If a car suddenly brakes, passengers continue to move forward due to their inertia.

Question 4

State Newton's Second Law of Motion.

Accepted Answer

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. It is expressed by the formula $F_{net} = ma$.

Question 5

Provide an example of Newton's Second Law.

Accepted Answer

Pushing a light shopping cart requires less force to accelerate it than pushing a heavily loaded cart to achieve the same acceleration. A larger net force on an object results in a larger acceleration.

Question 6

What is Newton's Third Law of Motion?

Accepted Answer

For every action, there is an equal and opposite reaction. When one object exerts a force on a second object, the second object simultaneously exerts a force equal in magnitude and opposite in direction on the first object.

Question 7

Provide an example of Newton's Third Law.

Accepted Answer

When you push against a wall, the wall pushes back on you with an equal and opposite force. A rocket expels gas downwards (action), and the gas exerts an upward force on the rocket (reaction), propelling it.

Question 8

Define work in physics.

Accepted Answer

Work ($W$) is done when a force causes a displacement of an object. It is the product of the component of the force in the direction of the displacement and the magnitude of the displacement. The formula is $W = Fd \cos 	heta$, where $F$ is force, $d$ is displacement, and $	heta$ is the angle between the force and displacement vectors.

Question 9

What are the SI units for work?

Accepted Answer

The SI unit for work is the Joule (J), which is equivalent to Newton-meter ($N \cdot m$).

Question 10

Define kinetic energy and provide its formula.

Accepted Answer

Kinetic energy ($KE$) is the energy an object possesses due to its motion. It depends on the object's mass and speed. The formula is $KE = \frac{1}{2}mv^2$, where $m$ is mass and $v$ is speed.

Question 11

What are the SI units for energy?

Accepted Answer

The SI unit for all forms of energy, including kinetic and potential energy, is the Joule (J).

Question 12

Define gravitational potential energy and provide its formula.

Accepted Answer

Gravitational potential energy ($PE_g$) is the energy an object possesses due to its position in a gravitational field, relative to a reference point. The formula is $PE_g = mgh$, where $m$ is mass, $g$ is the acceleration due to gravity, and $h$ is the height.

Question 13

Define elastic potential energy (spring potential energy) and provide its formula.

Accepted Answer

Elastic potential energy ($PE_s$) is the energy stored in an elastic material, such as a spring, when it is stretched or compressed from its equilibrium position. The formula is $PE_s = \frac{1}{2}kx^2$, where $k$ is the spring constant and $x$ is the displacement from equilibrium.

Question 14

State the Work-Energy Theorem.

Accepted Answer

The Work-Energy Theorem states that the net work done on an object is equal to the change in its kinetic energy. Mathematically, $W_{net} = \Delta KE = KE_f - KE_i$.

Question 15

Define power in physics and provide its formula.

Accepted Answer

Power ($P$) is the rate at which work is done or energy is transferred. It measures how quickly energy is used or converted. The formula is $P = \frac{W}{\Delta t}$ or $P = Fv \cos 	heta$.

Question 16

State the Principle of Conservation of Energy.

Accepted Answer

The Principle of Conservation of Energy states that energy cannot be created or destroyed, only transformed from one form to another. The total energy of an isolated system remains constant.

Question 17

What is mechanical energy and how is it conserved?

Accepted Answer

Mechanical energy ($ME$) is the sum of an object's kinetic energy and potential energy ($ME = KE + PE$). In the absence of non-conservative forces (like friction or air resistance), mechanical energy is conserved, meaning $ME_i = ME_f$ or $KE_i + PE_i = KE_f + PE_f$.

Question 18

Differentiate between conservative and non-conservative forces.

Accepted Answer

Conservative forces: Forces for which the work done in moving an object between two points is independent of the path taken (e.g., gravity, spring force).
Non-conservative forces: Forces for which the work done depends on the path taken, and they dissipate mechanical energy (e.g., friction, air resistance).

Question 19

State the Principle of Conservation of Momentum.

Accepted Answer

For an isolated system (where no external forces act), the total linear momentum of the system remains constant. In a collision or interaction, the total momentum before the event equals the total momentum after the event: $\sum p_{initial} = \sum p_{final}$.

Question 20

Define impulse and provide its formula.

Accepted Answer

Impulse ($J$) is the change in momentum of an object. It is also defined as the product of the average net force acting on an object and the time interval over which the force acts. The formula is $J = F_{avg} \Delta t = \Delta p$.

Question 21

State the Impulse-Momentum Theorem.

Accepted Answer

The Impulse-Momentum Theorem states that the impulse applied to an object is equal to the change in its momentum. Mathematically, $J = \Delta p = mv_f - mv_i$.

Question 22

What are the two main types of collisions in terms of energy conservation?

Accepted Answer

Elastic collision: A collision in which both momentum and kinetic energy are conserved. Objects bounce off each other.
Inelastic collision: A collision in which momentum is conserved, but kinetic energy is *not* conserved (some kinetic energy is converted to other forms, like heat or sound). Objects may stick together.

Question 23

What defines an "isolated system" in physics?

Accepted Answer

An isolated system is a system where no external forces act on it, or the net external force is zero. This is a crucial condition for the conservation of momentum and total energy.

Question 24

How does the concept of "system" apply to conservation laws?

Accepted Answer

A "system" is a defined collection of objects that we are interested in studying. Conservation laws (like energy and momentum) apply to the *total* energy or momentum of the system, not necessarily individual objects within it, especially if the system is isolated from external influences.

Classical Mechanics - Newtonian Laws & Energy Conservation

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