ACT Science time-saving strategy tips and practice

Newton's First Law

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

Acceleration formula

Acceleration ($\displaystyle a$) is the change in velocity ($\displaystyle \frac{ riangle v}{ riangle t}$).

True or False: Weight and mass are the same.

False. Weight is the force due to gravity acting on mass: $\displaystyle W = mg$.

Fill in the blank: The unit of force is _____

The unit of force is Newton (N).

Difference between distance and displacement?

Distance is total path traveled. Displacement is the straight line from start to end.

What does the slope of a velocity-time graph represent?

The slope represents acceleration. A steeper slope indicates greater acceleration.

Kinetic Energy Formula

Kinetic Energy ($\displaystyle KE$) is given by $\displaystyle KE = \frac{1}{2}mv^2$, where $\displaystyle m$ is mass and $\displaystyle v$ is velocity.

Cause → Effect: Applying brakes in a car

Cause: brakes applied → Effect: car decelerates due to friction.

True or False: A heavier object falls faster than a lighter one.

False. In free fall, all objects accelerate at the same rate (ignoring air resistance).

Potential Energy Formula

Potential Energy ($\displaystyle PE$) is given by $\displaystyle PE = mgh$, where $\displaystyle m$ is mass, $\displaystyle g$ is acceleration due to gravity, and $\displaystyle h$ is height.

What is the principle of conservation of energy?

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

Effect of increased mass on gravitational force?

Increased mass results in greater gravitational force between two objects, according to $\displaystyle F = G\frac{m_1 m_2}{r^2}$.

Name the three types of friction.

Static friction, kinetic friction, and rolling friction.

What is the Law of Universal Gravitation?

Every point mass attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

How do unbalanced forces affect motion?

Unbalanced forces result in a change in motion; they cause acceleration as per Newton's Second Law.

What is momentum?

Momentum ($\displaystyle p$) is the product of mass and velocity: $\displaystyle p = mv$. It is conserved in a closed system.

Newton's Second Law

The formula is $\displaystyle F = ma$. It states that force equals mass times acceleration.

What does $\displaystyle K.E. = \frac{1}{2}mv^2$ calculate?

It calculates kinetic energy, where $\displaystyle m$ is mass and $\displaystyle v$ is velocity.

True or False: Potential energy increases with height.

True. Gravitational potential energy $\displaystyle U = mgh$ increases as height $\displaystyle h$ increases.

Fill in the blank: $\displaystyle P = \frac{W}{t}$, where $\displaystyle P$ is ___

Power. $\displaystyle W$ is work done, $\displaystyle t$ is time.

Difference between speed and velocity?

Speed is scalar (magnitude only); velocity is vector (magnitude + direction).

Calculate work done: $\displaystyle W = Fd$.

Example: $\displaystyle F = 10 ext{ N}$, $\displaystyle d = 5 ext{ m}$. Work $\displaystyle W = 10 imes 5 = 50 ext{ J}$.

What is the formula for gravitational force?

$\displaystyle F_g = \frac{G m_1 m_2}{r^2}$, where $\displaystyle G$ is the gravitational constant.

Cause → Effect: Increase in mass leads to ___

Higher gravitational force, according to $\displaystyle F_g = mg$.

What is the formula for acceleration?

$\displaystyle a = \frac{ riangle v}{ riangle t}$, where $\displaystyle riangle v$ is change in velocity.

True or False: Work can be negative.

True. Work is negative when force opposes motion.

Pressure formula?

$\displaystyle P = \frac{F}{A}$, where $\displaystyle F$ is force applied and $\displaystyle A$ is area.

Define momentum.

Momentum $\displaystyle p = mv$, the product of mass and velocity.

What is Hooke's Law?

$\displaystyle F = -kx$, where $\displaystyle F$ is restoring force, $\displaystyle k$ is spring constant, $\displaystyle x$ is displacement.

Calculate potential energy: $\displaystyle U = mgh$.

Example: $\displaystyle m = 2 ext{ kg}$, $\displaystyle g = 9.8 ext{ m/s}^2$, $\displaystyle h = 3 ext{ m}$. $\displaystyle U = 2 imes 9.8 imes 3 = 58.8 ext{ J}$.

What does a slope represent in a distance-time graph?

The slope represents speed. A steeper slope indicates higher speed.

True or False: A horizontal line indicates constant acceleration.

False. A horizontal line indicates constant velocity, not acceleration.

Fill in the blank: In a velocity-time graph, the area under the curve represents _____

displacement.

Compare linear and non-linear graphs.

Linear graphs show constant rates; non-linear graphs show changing rates.

What does a negative slope indicate in a speed-time graph?

It indicates deceleration or negative acceleration.

How do you determine acceleration from a velocity-time graph?

Acceleration is the slope of the velocity-time graph.

Cause → Effect: Increasing force on an object results in _____

increased acceleration (Newton's Second Law).

What information can be derived from a graph's intercept?

The intercept can indicate initial conditions, like starting velocity.

True or False: The area between two lines in a graph always represents a physical quantity.

True. It often represents a change in a physical quantity over time.

What does a curved line on a position-time graph indicate?

It indicates changing velocity (acceleration).

Example: Calculate the average speed if distance is 100 miles in 2 hours.

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

Identify the key elements in a force vs. displacement graph.

- Slope indicates work done. - Area represents energy transferred.

What does a steep curve indicate in a speed-time graph?

It indicates higher acceleration.

Fill in the blank: In mechanics, a graph’s axis labels must include _____

units of measurement (e.g., m, s, N).