Force and Motion Basics
What is defined as a push or a pull on an object?
What is a Force?
What is the net force acting on an object when the forces are balanced?
0 Newtons
What is the total overall force acting on an object called?
What if Net Force?
What type of force requires physical contact between two objects to occur?
Contact force
What is the difference between static friction and sliding friction?
Static friction resists the initial movement of a stationary object; sliding friction resists the motion of an object already sliding. (Static friction is generally stronger than sliding friction).
State Newton’s First Law of Motion.
An object at rest stays at rest, and an object in motion stays in motion at a constant velocity, unless acted upon by an unbalanced external force.
What is the term for a change in an object's position relative to a reference point over time?
What is motion?
What happens to an object’s motion when acted upon by unbalanced forces?
The object's motion changes.
If two forces of 10N and 15N push a box to the right, what is the net force?
25N
Give two examples of non-contact forces.
Gravity, magnetic, or static electricity
A heavy crate remains stationary when you push it with $40\text{ N}$ of force. What is the magnitude of the static friction force?
40N
What is inertia?
Inertia is the natural tendency of an object to resist any change in its state of motion.
What is an action where two or more objects exert forces on each other?
What is an interaction?
A book rests stationary on a table. Are the forces acting on it balanced or unbalanced?
A team pulls a rope to the left with 80N of force, while another team pulls to the right with 60N. What is the net force?
20N
Is friction classified as a contact or non-contact force? Explain why.
Contact force; it occurs due to physical contact and microscopic interactions between two surfaces touching each other.
In a Free-Body Diagram, what do the length and arrowhead of a force vector represent?
Length represents the magnitude (strength) of the force, and the arrowhead represents the direction of the force.
(not on the quiz) What physical property of an object determines how much inertia it has?
Its Mass (more mass = more inertia).
Why is a reference point necessary when describing the direction of an object's motion?
Motion is relative; a reference point provides a fixed frame of reference to determine if, how fast, and in what direction an object is moving.
A satellite travels at a constant velocity in deep space. Are the net forces acting on it zero or non-zero?
Zero
A box has forces of of 20 N left and 5 N right. Calculate the magnitude and determine the direction of the net force.
15 N left
Explain why friction occurs when two surfaces slide against each other.
At a microscopic level, all surfaces have tiny bumps and ridges. When surfaces slide past each other, these bumps collide and interlock, resisting motion.
Describe two of the arrowson a Free-Body Diagram for a car sliding to a stop on a flat road.
Friction pointing Backward/Opposite to motion
No forward applied force arrow (or a smaller forward arrow if coasting).
Using the concept of inertia, explain why a crash test dummy lurches forward when a car abruptly stops.
The dummy was moving forward at the car's speed. Due to inertia, the dummy tends to remain in forward motion at that same speed until an unbalanced force (like a seatbelt or airbag) acts on it to stop it.
(you won't see something like this on the quiz) A car moves at +50 mph relative to the road, while a truck travels in the opposite direction at 40 mph. Describe the truck’s velocity relative to the car using a directional reference.
-90 mph (or 90 mph in the opposite/negative direction relative to the car).
An object moving at 5 m/s to the right suddenly speeds up to 12 m/s. Identify if the forces are balanced or unbalanced, and state the direction of the net force.
Unbalanced, net force directed to the right
A sled is pulled with 50N forward against a friction force of 15N and air resistance of 10N. Calculate the net force.
25 N
Name two factors that decrease friction in practical situations.
Decrease: Lubricants (oil, grease), smoothing, using wheels/ball bearings.
A 100N box slides across a floor at constant speed when pushed with 30N to the right. Draw/describe the complete Free-Body Diagram with all force values labeled.
Fa=30N right
How does Newton's First Law explain why an astronaut floating in deep space keeps moving forever without burning fuel?
In deep space, there is virtually no friction or gravity (net force = 0 N). Because forces are balanced, the astronaut maintains a constant velocity indefinitely according to Newton's 1st Law.