Newton’s Laws & Kinematics Summative Exam (9th Grade Physics & Earth Science)

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Instrukcije

Assess students’ understanding of Newton’s three laws, force calculations, and kinematics (speed, velocity, acceleration, distance, time). Calculator and unit conversions allowed. Includes conceptual, computational, and short-answer items.

Title: Newton’s Laws & Kinematics Summative Exam (9th Grade Physics & Earth Science)

Description: Assess students’ understanding of Newton’s three laws, force calculations, and kinematics (speed, velocity, acceleration, distance, time). Calculator and unit conversions allowed. Includes conceptual, computational, and short-answer items.

Questions:

Multiple Choice: Which statement best describes Newton’s First Law (the law of inertia)?

An object at rest stays at rest unless acted on by an unbalanced force. (Correct)
Forc es always come in equal and opposite pairs.
Force equals mass times acceleration.
Acceleration is proportional to the square of speed.

Multiple Choice: An astronaut in deep space (no external forces) pushes a tool away. What happens to the astronaut?

The astronaut remains stationary because of inertia.
The astronaut moves in the opposite direction. (Correct)
The astronaut moves in the same direction as the tool.
The astronaut floats without moving because of zero gravity.

Multiple Choice: Which is an example of Newton’s Third Law?

A book sliding to a stop due to friction.
A rocket accelerating as gas is expelled backward. (Correct)
A car moving at constant velocity on a flat road.
A ball sitting on a table.

Multiple Selection: Which two factors directly affect the acceleration of an object according to Newton’s Second Law?

Net force on the object (Correct)
Mass of the object (Correct)
Initial velocity of the object
Volume of the object

True or False: If net force on an object is zero, its velocity must be zero.

False (Correct)

Multiple Choice: A 2.0 kg cart experiences a net force of $10$ N. What is its acceleration?

$2.0\ \text{m/s}^2$ (Correct)
$5.0\ \text{m/s}^2$
$0.20\ \text{m/s}^2$
$12\ \text{m/s}^2$

Short Answer: Write the formula that relates force, mass, and acceleration.

$F=ma$ (Correct)

Numeric: A 1500 kg car accelerates at $3$ m/s^2. Compute the net force.

Answer (LaTeX): 1500\times3

Multiple Choice: A runner increases speed from $2$ m/s to $6$ m/s in $4$ s. What is the runner’s acceleration?

$1.0\ \text{m/s}^2$
$2.0\ \text{m/s}^2$ (Correct)
$0.5\ \text{m/s}^2$
$8.0\ \text{m/s}^2$

Multiple Choice: A car travels at constant speed around a circular track. Which is true?

There is no acceleration because speed is constant.
There is acceleration because velocity direction changes. (Correct)
The net force is zero.
Only gravitational force acts on the car.

Multiple Choice: Which diagram correctly shows forces on a book at rest on a table? (best description)

Upward normal force equal to downward weight. (Correct)
Upward normal larger than weight.
Downward normal and upward weight.
No forces act on the book.

Multiple Choice: A 5.0 N horizontal force is applied to a 2.0 kg block on a frictionless surface. What is the acceleration?

$2.5\ \text{m/s}^2$ (Correct)
$0.40\ \text{m/s}^2$
$7.0\ \text{m/s}^2$
$10\ \text{m/s}^2$

Multiple Choice: Which best explains why seat belts reduce injuries in a car crash?

They increase the car’s mass.
They reduce friction inside the car.
They apply an unbalanced force to change passenger momentum more slowly. (Correct)
They eliminate all forces on the passenger.

Multiple Choice: A box slides across a rough floor at constant velocity. What is true about the forces?

Applied force equals friction force. (Correct)
Applied force is greater than friction force.
Friction force is zero.
Normal force is greater than weight.

Short Answer: State Newton’s Second Law in words (three words or less).

Force causes acceleration (Correct)

Multiple Choice: A ball is thrown upward. At the top of its path, its instantaneous velocity is zero. Which is true about acceleration at that instant?

Acceleration is zero because velocity is zero.
Acceleration is downward due to gravity. (Correct)
Acceleration is upward to stop the ball.
Acceleration is sideways.

Multiple Choice: A car goes from rest to a speed of $20\ \text{m/s}$ in $10$ s. What is the average acceleration?

$2.0\ \text{m/s}^2$ (Correct)
$0.5\ \text{m/s}^2$
$200\ \text{m/s}^2$
$10\ \text{m/s}^2$

Numeric: A cyclist travels at average speed $12\ \text{m/s}$ for $15$ s. How far do they travel?

Answer (LaTeX): 12\times15

Multiple Choice: Which expression gives displacement for constant acceleration starting from rest?

$x=\frac{1}{2}at^2$ (Correct)
$x=at$
$x=vt+ \tfrac{1}{2}gt^2$
$x=vt^2$

Multiple Selection: Which quantities are vectors?

Speed
Velocity (Correct)
Acceleration (Correct)
Distance

Matching: Left: A spacecraft coasts in space with no engine thrust. / A swimmer pushes water backward and moves forward. / A heavier object requires more push to reach the same acceleration. Right: Newton’s First Law (inertia) / Newton’s Second Law (F=ma) / Newton’s Third Law (action-reaction)

Answers: spacecraft — Newton’s First Law (inertia) (Correct); swimmer — Newton’s Third Law (action-reaction) (Correct); heavier object — Newton’s Second Law (F=ma) (Correct).

Multiple Choice: A block on an incline has weight $mg$. Which component causes it to slide down the incline (angle $\theta$)?

$mg\cos\theta$
$mg\sin\theta$ (Correct)
$mg$
Normal force

Long Answer: A 10.0 kg crate is pulled along a horizontal floor with 60.0 N applied. The kinetic friction force is 20.0 N. Calculate the acceleration and describe how Newton’s Second Law applies.

Correct answer (one paragraph or less): Net force = $60.0-20.0=40.0\ \text{N}$. Acceleration = $a=\dfrac{F_{net}}{m}=\dfrac{40.0}{10.0}=4.0\ \text{m/s}^2$. Newton’s Second Law applies because the net unbalanced force produces the computed acceleration proportional to the net force and inversely proportional to mass. (Correct)

Multiple Choice: A car braking applies a backward force causing acceleration of $-6\ \text{m/s}^2$. If the car’s mass is $1000\ \text{kg}$, what is the braking force?

$-6000\ \text{N}$ (Correct)
$-166.7\ \text{N}$
$-600\ \text{N}$
$-60000\ \text{N}$

Show Your Work: Design a brief procedure (2–3 steps) to measure acceleration of a small cart on a flat track using a stopwatch and meterstick. Explain what measurements you will take and the calculation you will perform.

Example correct response (concise): 1) Measure distance $d$ the cart travels from rest in measured time $t$. 2) Record $d$ and $t$ for several trials. 3) Calculate acceleration using $d=\tfrac{1}{2}at^2$, so $a=\dfrac{2d}{t^2}$. Explain averaging trials for accuracy. (Correct)

Formative categories: Conceptual; Calculations; Representations