Physics Module 2 Review: Acceleration, Free Fall, and Newton's Laws

Flashcards covering Physics Module 2 review topics: manipulating equations, acceleration, motion graphs, free fall, and Newton's laws of motion.

How is the equation $d = \frac{1}{2}at^2$ solved for acceleration ($a$)?

$$a = \frac{2d}{t^2}$$

How is the equation $T = 2\pi\sqrt{\frac{L}{g}}$ solved for length ($L$)?

$$L = \frac{T^2 g}{4\pi^2}$$

What is the definition of acceleration?

Acceleration is the rate of change of velocity (or the change in velocity over the change in time).

What is non-accelerated motion?

Non-accelerated motion is when the motion of an object is not speeding up, slowing down, or changing direction.

What is accelerated motion?

Accelerated motion is when the motion of an object is speeding up, slowing down, and/or changing direction.

What are the three ways the velocity of an object changes, indicating acceleration has occurred?

a. change in speed; b. change in direction; c. change in both speed and direction

What are the three kinematic equations that contain initial velocity ($v_o$)?

a. $d = v_o t + \frac{1}{2}at^2$; b. $v_f^2 = v_o^2 + 2ad$; c. $a = \frac{v_f - v_o}{t}$

What are the three kinematic equations rewritten assuming the initial velocity ($v_o$) is $0$?

a. $d = \frac{1}{2}at^2$; b. $v_f = 2ad$; c. $a = \frac{v_f}{t}$

A truck starts from rest at a stop light and accelerates at $5.2\,\text{m/s}^2$ for $3.5\,\text{s}$. How far did the truck travel from the stop light?

$$32\,\text{m}$$

Allyson is riding a bike and starts slowing down with an average acceleration of $-1.5\,\text{m/s}^2$. If her initial velocity was $6.5\,\text{m/s}$, how far does she travel in $2.5\,\text{seconds}$?

$$12\,\text{m}$$

Based on the position vs. time graph, what is the change in position during the fourth hour of the trip (from $t = 3\,\text{hour}$ to $t = 4\,\text{hour}$)?

$$0\,\text{m}$$

Based on the position vs. time graph, what is the change in position during the seventh hour of the trip (from $t = 6\,\text{hour}$ to $t = 7\,\text{hour}$)?

$$-40\,\text{m}$$

Based on the acceleration vs. time graph, what is the change in velocity during the first $10\,\text{seconds}$?

$$125\,\text{m/s}$$

Based on the acceleration vs. time graph, what is the change in velocity from $50\,\text{seconds}$ to $70\,\text{seconds}$?

$$0\,\text{m/s}$$

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

speed

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

acceleration

What does the area under an acceleration-time graph represent?

change in speed

What does the area under a velocity-time graph represent?

displacement

What is the definition of free-fall motion?

Free-fall motion is when an object is falling under the influence of gravity only.

What is the value of acceleration due to gravity on Earth?

$$9.8\,\text{m/s}^2$$

What is the difference between mass and weight?

Mass is the amount of matter in an object while weight is the measure of gravitational force acting on an object.

A feather and a brick are dropped from the same height at the same time in free-fall motion. Which one will reach the ground first?

Neither. They will land on the ground at the same time because in free-fall motion ALL objects accelerate at the same rate.

Does air resistance affect objects that are in free-fall motion?

No. In free-fall motion, all objects accelerate at the same rate and are only under the influence of a gravitational force.

A ball is dropped from a height of $450\,\text{meters}$ in free-fall motion. How long will it take the ball to first strike the ground?

$$9.6\,\text{seconds}$$

A ball is dropped from an unknown height in free-fall motion. If it takes $8.9\,\text{seconds}$ to strike the ground, what was the height of the building?

$$388\,\text{meters}$$

According to Newton, what two factors does gravity depend on?

The mass and the distance between them.

What does it mean that the force of gravity follows an inverse-squared relationship with distance?

The intensity of the force of gravity is inversely proportional to the square of the distance between two objects.

What effect does increasing the mass of one or both objects have on the gravitational force between them?

Increasing the mass of one or both objects will cause an increase in the gravitational force between the two objects.

How does increasing or decreasing the distance between two objects affect the gravitational force between them?

Increasing the distance between two objects will decrease the gravitational force between them and decreasing the distance between the two objects will increase the gravitational force between them.

What is the definition of Newton's First Law?

An object at rest will stay at rest unless acted upon by an unbalanced force and an object in motion in a straight line and at a constant speed will remain in that state of motion unless acted upon by an unbalanced force.

What is inertia?

Inertia is the tendency of an object to resist a change in its state of rest or motion. The greater the mass of an object the greater the force needed to change the object's motion.

What is the definition of net force?

The net force is the sum of all forces acting on an object.

What is the magnitude of acceleration if the net force is equal to zero?

$$0\,\text{m/s}^2$$

What is the state of forces when the net force equals $0\,\text{(zero)}$ versus when it does not equal $0$?

When the net force equals $0\,\text{(zero)}$ we say that there are balanced forces, or equilibrium. When the net force does not equal $0$, we say there are unbalanced forces.

Is force a scalar or a vector quantity, and what is its unit?

Force is a vector quantity, and its unit is the Newton ($\text{N}$).

What is the definition of Newton's Third Law?

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

Why do action and reaction forces not cancel each other out?

They do not cancel each other out because they are acting on different objects. Object A is exerting a force on object B and object B is exerting a force on object A.

What are the action and reaction forces when you kick a soccer ball that is at rest on the ground?

Action: you kick the ball. Reaction: the ball “kicks” you back.

What are the action and reaction forces when you set a glass down on a table?

Action: the weight (gravitational force) of the glass pushes down on the table. Reaction: the table pushes back up on the glass (normal force).

What does Newton's second law state?

Newton’s second law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to the mass of the object.

What is the equation for Newton's 2nd Law solved for acceleration ($a$) and force ($F$)?

$a = \frac{F}{m}$ or $F = ma$

What are the standard units for acceleration, force, and mass?

a. acceleration: $\text{m/s}^2$ (meters per second squared); b. force: $\text{N}$ (Newtons); c. mass: $\text{kg}$ (kilograms)

Layla is driving at $15\,\text{m/s}$ when she decides to speed up to $29\,\text{m/s}$. If it takes her $3.2\,\text{seconds}$ to reach her new speed, what was the magnitude of the acceleration?

$$4.4\,\text{m/s}^2$$

Haley's new scooter, starting from rest, can reach a speed of $8.90\,\text{m/s}$ in about $3.56\,\text{s}$. If the combined mass of Haley and her scooter is $225\,\text{kg}$, what is the magnitude of the unbalanced force required to accelerate her and the scooter at this rate?

$$563\,\text{N}$$

Kally and her teammate are pushing a bobsled at the beginning of a race with a force of $620\,\text{N}$ that causes an acceleration of $4.8\,\text{m/s}^2$. What is the mass of the bobsled?

$$130\,\text{kg}$$