Newton's First Law
Define Newton's First Law in one sentence.
An object in motion will stay in motion, and an object at rest will stay at rest unless acted upon by an outside (net) force.
State Newton's Second Law as a formula and name each variable and its SI unit
Formula: F=ma . Variables: F is net force (SI unit: newton, N), m is mass (SI unit: kilogram, kg), a is acceleration (SI unit: m/s2 )
State Newton's Third Law in one sentence.
For every action, there is an equal and opposite reaction.
What is meant by "net force"? How does net force relate to acceleration?
Net force is the vector sum of all forces acting on an object. The net force determines the object's acceleration according to Fnet=ma ; if Fnet=0, acceleration is zero.
What is the hardest substance in the human body
What is inertia? Give an example!
Inertia is the property of an object that resists changes in its motion. Example: A shopping cart full of groceries is harder to start or stop than an empty cart because the full cart has more inertia
A 10 kg cart is pushed with a force of 20 N. What is the cart’s acceleration?
In an action-reaction pair, do the two forces act on the same object or different objects? Explain why they do not cancel each other.
They act on different objects. They don't cancel because cancellation requires forces to act on the same object; action and reaction act on two different bodies, so each object feels only one of the forces in the pair when considering forces on that object.
Identify whether acceleration is directly or inversely related to (a) net force and (b) mass. Provide a one-sentence justification each.
(a) Acceleration is directly proportional to net force — doubling net force (with mass constant) doubles acceleration because a=Fnetm
(b) Acceleration is inversely proportional to mass — increasing mass (with force constant) decreases acceleration because a=Fnetm
How many bones do sharks have?
0(their skeletons are made of cartilage)
During a science lab, a student quickly pulls a tablecloth out from under a set of dishes without breaking them. The dishes remain nearly in place even though the cloth moves rapidly. Why did the dishes resist changing their state of rest?
INERTIA
A 5 kg backpack accelerates at 3 m/s².What force is acting on the backpack?
15 N
When a bug traveling west collides with the windshield of a car traveling east, which of these is true and why? (a) the bug experiences a stronger force than the car. (b) the bug and car experience the same size force. (c) the car accelerates more than the bug. (d) the bug does not accelerate due to the force
B
Calculate the acceleration of a truck with a mass of 5000 kg when its brakes apply a net force of 15,000 N. Show work.
3 m/s2
Roughly how long does it take for the sun's light to reach Earth?
8 mins
An object is moving at a constant 50 m/s. A 10 N force pushes left while a 10 N force pushes right. Draw or describe the free-body situation and state the object's velocity after 30 seconds. Explain using Newton's First Law.
50 m/s because the object is moving at a constant rate and there is nothing opposing the force to slow it down or change directions. The forces are BALANCED
Two students push a 40 kg box. The total force applied is 80 N. What is the box’s acceleration?
2 m/s2
When an object is more massive, what happens to its acceleration?
it is less massive
A student writes that as mass decreases, inertia decreases and that this relationship is "directly proportional." Is that correct? Explain the relationship between mass and inertia and justify the term "directly proportional" or "inversely proportional."
That is correct: inertia increases with mass and decreases as mass decreases. This is a direct (positive) proportional relationship: objects with larger mass have proportionally greater inertia because mass quantifies the amount of inertia an object has
What percentage of Earth's water is salt water
97%
Explain why wearing a seatbelt in a car is an application of Newton's First Law. Include the roles of inertia and net force in your answer.
In a crash or sudden stop, your body tends to continue moving forward (inertia). The seatbelt provides an external force to stop your motion safely (produces the net force on your body), preventing you from continuing forward into the windshield. Without the seatbelt, there would be little net force acting on you to stop your motion until you hit something unsafe.
A soccer ball with a mass of 0.5 kg is kicked and accelerates at 10 m/s². How much force was applied to the ball?
5 N
Two vehicles collide: a large truck and a small car. The forces on each vehicle are equal and opposite. Explain why the small car typically experiences a larger change in velocity (and more damage). Use Newton's laws and discuss mass and acceleration
The forces are equal and opposite, acceleration depends on mass via a=F/m. For the same magnitude force, the smaller-mass car will have a larger acceleration (change in velocity) than the heavier truck, leading to more rapid deceleration and typically more damage to the smaller vehicle.
Force of Gravity (Down)
Normal Force (Up)
Applied Force (Push)
Friction Force (Pull)
What does a Geiger counter measure?
Radiation