ACT Science research summaries flashcards

What is displacement?

Displacement is the change in position of an object. It is a vector quantity that has both magnitude and direction.

Define velocity.

Velocity is the rate at which an object changes its position. It is a vector quantity, expressed as: $\displaystyle v = \\frac{\Delta x}{\Delta t}$.

True or False: Speed is a vector quantity.

False. Speed is a scalar quantity that only measures how fast an object is moving, without direction.

What is acceleration?

Acceleration is the rate of change of velocity over time. It can be calculated using: $\displaystyle a = \\frac{\Delta v}{\Delta t}$.

Fill in the blank: The unit of velocity is _____.

meters per second (m/s) or miles per hour (mph).

Compare speed and velocity.

Speed: scalar, magnitude only. Velocity: vector, magnitude and direction.

What is uniform motion?

Uniform motion occurs when an object travels equal distances in equal intervals of time, with constant velocity.

Cause → Effect: If an object accelerates, what happens to its velocity?

The velocity of the object changes; it increases if acceleration is positive, decreases if negative.

Calculate the average speed: 100 miles in 2 hours.

Average speed = distance / time = $\displaystyle \\frac{100 \text{ miles}}{2 \text{ hours}} = 50 \text{ mph}$.

What is the equation for displacement in constant acceleration?

Displacement can be calculated using the formula: $\displaystyle d = v_i t + \\frac{1}{2} a t^2$, where $\displaystyle v_i$ is initial velocity.

True or False: An object can be accelerating while moving at constant speed.

True. An object can accelerate by changing direction while maintaining constant speed, e.g., moving in a circle.

What is instantaneous velocity?

Instantaneous velocity is the velocity of an object at a specific moment in time, often measured using calculus.

List the units of acceleration.

Units: meters per second squared (m/s²) or feet per second squared (ft/s²).

Fill in the blank: Velocity is positive when moving _____.

in the positive direction or forward.

What is the relationship between distance, speed, and time?

Distance = speed × time, or $\displaystyle d = vt$.

How does gravity affect falling objects?

Gravity causes objects to accelerate downwards at approximately $\displaystyle 9.8 ext{ m/s}^2$ near Earth's surface.

What is Newton's First Law of Motion?

An object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net external force.

True or False: Gravity is a contact force.

False. Gravity is a non-contact force that acts at a distance.

Fill in the blank: The unit of force in the SI system is the __________.

Newton (N) - defined as $\displaystyle ext{kg} imes ext{m/s}^2$.

What is the formula for force?

$\displaystyle F = ma$, where $\displaystyle F$ is force, $\displaystyle m$ is mass, and $\displaystyle a$ is acceleration.

Compare mass and weight.

Mass is the amount of matter in an object (kg), while weight is the gravitational force acting on that mass (N).

What does Newton's Second Law state?

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

Cause → Effect: Applying a greater force results in __________.

Greater acceleration, as per Newton's Second Law.

How does friction affect motion?

Friction opposes the motion of objects, reducing acceleration and velocity.

What is the difference between static and kinetic friction?

Static friction acts on stationary objects; kinetic friction acts on moving objects, typically with less magnitude.

True or False: All forces act in pairs.

True. According to Newton's Third Law, every action has an equal and opposite reaction.

What is the net force if two equal forces act in opposite directions?

The net force is zero, resulting in no acceleration.

Fill in the blank: The gravitational force between two objects depends on their __________ and the distance between them.

Masses.

What does Newton's Third Law state?

For every action, there is an equal and opposite reaction.

Cause → Effect: Increasing mass while keeping force constant results in __________.

Decreased acceleration.

Example: A 10 kg object accelerates at 2 m/s². What is the force?

$\displaystyle F = ma = 10 ext{ kg} imes 2 ext{ m/s}^2 = 20 ext{ N}$.

What is an example of a contact force?

Friction, tension, and normal force are all examples of contact forces.

What is the law of conservation of energy?

Energy cannot be created or destroyed, only transformed from one form to another.

Define work in physics.

Work is done when a force causes displacement. Formula: $\displaystyle W = F imes d imes ext{cos}( heta)$.

True or False: Work can be done without movement.

False. Work requires displacement; no movement means no work.

Fill in the blank: Kinetic energy is given by the formula __________.

$\displaystyle KE = \frac{1}{2}mv^2$.

How do potential and kinetic energy compare?

Potential energy is stored energy; kinetic energy is energy of motion.

Calculate work: 10 N force moves 5 m.

$\displaystyle W = F imes d = 10 imes 5 = 50 ext{ J}$.

What is power in the context of work?

Power is the rate at which work is done. Formula: $\displaystyle P = \frac{W}{t}$.

True or False: Power is measured in Joules.

False. Power is measured in Watts (W), where 1 W = 1 J/s.

What is gravitational potential energy?

Gravitational potential energy depends on height. Formula: $\displaystyle PE = mgh$.

Example: What is the potential energy of a 2 kg object at 3 m?

$\displaystyle PE = mgh = 2 imes 9.8 imes 3 = 58.8 ext{ J}$.

Cause → Effect: Increasing height affects energy how?

Increasing height increases gravitational potential energy.

Differentiate between elastic and inelastic potential energy.

Elastic potential energy stores energy in deformed objects; inelastic doesn't recover shape.

What is the unit of work?

The unit of work is the Joule (J). 1 J = 1 N·m.

Calculate power: 200 J of work in 4 seconds.

$\displaystyle P = \frac{W}{t} = \frac{200 ext{ J}}{4 ext{ s}} = 50 ext{ W}$.

What does a negative work value indicate?

Negative work indicates that the force opposes the direction of displacement.

Define mechanical energy.

Mechanical energy is the sum of kinetic and potential energy in a system.

What is momentum?

Momentum is the product of an object's mass and its velocity. Formula: $\displaystyle p = mv$.

True or False: Momentum is a scalar quantity.

False. Momentum is a vector quantity, having both magnitude and direction.

Fill in the blank: Impulse equals change in ___.

Impulse equals change in momentum.

What is impulse?

Impulse is the product of force and the time duration over which the force acts. Formula: $\displaystyle J = F imes t$.

Comparison: Elastic vs Inelastic Collisions.

Elastic collisions conserve kinetic energy; inelastic collisions do not.

Calculate the momentum: 5 kg object at 3 m/s.

Momentum = $\displaystyle p = mv = 5 imes 3 = 15 \, kg \, m/s$.

Define conservation of momentum.

In a closed system, the total momentum before a collision equals the total momentum after.

Question: What happens during an inelastic collision?

Kinetic energy is not conserved; objects may stick together.

Effect of increased mass on momentum?

Increased mass leads to increased momentum if velocity remains constant.

What is the formula for momentum?

The formula for momentum is $\displaystyle p = mv$, where $\displaystyle p$ is momentum, $\displaystyle m$ is mass, and $\displaystyle v$ is velocity.

Cause → Effect: High impulse results in ___ momentum change.

High impulse results in a large momentum change.

True or False: All collisions are perfectly elastic.

False. Most collisions are inelastic, losing some kinetic energy.

What is a perfectly elastic collision?

A collision where both momentum and kinetic energy are conserved.

Define impulse-momentum theorem.

Impulse is equal to the change in momentum: $\displaystyle J = riangle p$.

Calculate total momentum of two cars: 1200 kg at 20 m/s and 800 kg at 30 m/s.

Total momentum = $\displaystyle 1200 imes 20 + 800 imes 30 = 24000 + 24000 = 48000 \, kg \, m/s$.

Fill in the blank: Inelastic collisions often result in ___ deformation.

Inelastic collisions often result in permanent deformation.