MCAT work energy and power key terms

What is work in physics?

Work is defined as the product of force and displacement in the direction of the force. Formula: $\displaystyle W = F imes d$.

Fill in the blank: Work is measured in _____.

Joules (J).

True or False: Work can be done without displacement.

False. Work requires displacement in the direction of the applied force.

What is kinetic energy (KE)?

Kinetic energy is the energy of an object due to its motion. Formula: $\displaystyle KE = \\frac{1}{2}mv^2$.

Potential energy (PE) depends on which factors?

Mass, height, and gravitational acceleration. Formula: $\displaystyle PE = mgh$.

What is the relationship between work and energy?

Work done on an object results in a change in its energy. Work can increase or decrease energy.

Example: Calculate work done by a 10 N force over 5 meters.

Work = $\displaystyle W = F \times d = 10 \, N \times 5 \, m = 50 \, J$.

What type of energy is stored in a compressed spring?

Elastic potential energy.

Cause → Effect: Lifting an object increases its _____.

Potential energy.

Difference: Kinetic energy vs. Potential energy.

- Kinetic: energy of motion. - Potential: stored energy based on position.

What is the unit of energy?

Joule (J), equivalent to one Newton meter (N·m).

True or False: An object can have both kinetic and potential energy.

True. An object can possess both types simultaneously, e.g., a ball at the top of a hill.

What is gravitational potential energy?

Energy an object has due to its height above the ground. Formula: $\displaystyle PE = mgh$.

Comparison: Work vs. Energy.

- Work: process of energy transfer. - Energy: capacity to do work.

What happens to energy in a closed system?

Energy is conserved; it changes forms but remains constant overall.

Fill in the blank: The work-energy principle states that the total work done is equal to the change in _____.

Kinetic energy.

What is power?

Power is the rate at which work is done or energy is transferred. It is measured in watts (W).

Calculate power: 100 J in 5 seconds.

Power = Work / Time = 100 J / 5 s = 20 W.

True or False: Power and energy are the same.

False. Power is the rate of energy transfer, while energy is the capacity to do work.

Fill in the blank: Efficiency = (___) / (input energy).

Efficiency = (output energy) / (input energy).

What units measure efficiency?

Efficiency is often expressed as a percentage (%).

Cause → Effect: High power output.

High power output results in quicker work done in less time.

Compare: Mechanical Power vs. Electrical Power.

- Mechanical: Force times velocity (P = Fv). - Electrical: Voltage times current (P = VI).

What is the formula for efficiency?

Efficiency (%) = (Useful output energy / Total input energy) × 100.

Example: A machine outputs 150 J from 200 J input.

Efficiency = (150 J / 200 J) × 100 = 75%.

What does a watt represent?

A watt (W) represents one joule of energy transferred per second.

True or False: Higher efficiency means less waste.

True. Higher efficiency indicates that more input energy is converted into useful work.

What is a common real-world example of power?

A light bulb using 60 watts consumes energy quickly, illuminating a room effectively.

What is the law of conservation of energy?

Energy cannot be created or destroyed; it can only change forms. Example: Potential energy converts to kinetic energy.

True or False: Momentum is conserved in all collisions.

False. Momentum is conserved only in isolated systems without external forces.

Fill in the blank: Kinetic energy is given by ______.

The formula: $\displaystyle KE = \\frac{1}{2}mv^2$ where m is mass and v is velocity.

Momentum is defined as _____.

The product of mass and velocity: $\displaystyle p = mv$.

What happens to mechanical energy in a closed system?

Mechanical energy remains constant. It is the sum of potential and kinetic energy.

Cause → Effect: When a moving object collides with another object.

The total momentum before the collision equals the total momentum after.

Comparison: Elastic vs. Inelastic collisions.

Elastic: Total kinetic energy conserved. Inelastic: Some kinetic energy transforms into other forms.

What is impulse?

Impulse is the change in momentum, calculated as $\displaystyle J = F \Delta t$, where F is force and t is time.

When is mechanical energy not conserved?

When non-conservative forces, like friction, do work on the system.

True or False: Energy can be transformed from kinetic to potential.

True. Example: A roller coaster converting speed at the top of a hill.

What is the principle of conservation of momentum?

In an isolated system, the total momentum before an event equals the total after.

Example of conservation of energy in daily life.

A swinging pendulum: Energy transfers between potential and kinetic but total remains constant.