AP Physics 1 Exam

2021 AP Physics 1 Exam Study Guides + Unit Reviews | Fiveable

AP Physics 1

Free Reviews 2020

AP Physics Essentials

Unit 1: Kinematics

Unit 2: Dynamics

Unit 3: Circular Motion

Unit 4: Energy

Unit 5: Momentum

Unit 6: Simple Harmonic Motion

Unit 7: Torque & Rotational Motion

Unit 8: Electric Charges & Electric Force

Unit 9: DC Circuits

Unit 10: Mechanical Waves & Sound

Free Response Questions (FRQs)

Multiple Choice Questions (MCQs)

Blogs

Q & A sessions

Big Reviews: Finals & Exam Prep

Live Cram Sessions 2020

Using Momentum and Energy Concepts together to solve FRQ problems

Momentum & Energy Combo Problems

Momentum & Energy Combo Problems - Stream Slides

A review of momentum concepts including conservation of momentum and impulse graphs

Conservation of Momentum

Presentation Slides, Conservation of Momentum

 is defined as the product of the mass m and the velocity v of an object which in equation form is 

. The change in momentum of an object is a vector in the direction of the net force that's being exerted on the object. The units are 

It’s important to note that a constant linear momentum p is the momentum of an object of mass m that is moving in a straight line with a velocity v. Remember that the 

 and so is the momentum whereas the mass is a scalar. Momentum can also be applied to objects that are rotating or that have a torque acting upon them. If questions are referring to rotating objects, then the problems will specify 

When you solve for linear momentum in any question, be consistent with the direction you choose to be negative. For example, if you choose to make downwards negative, keep that direction negative throughout the problem. Be sure to consider the direction of the velocity. 

To find the total momentum, you should find the momentum of all directions and then find the sum of the momentum. 

Total Momentum = p1 + p2 + p3 ..., etc. 

Newton’s 2nd Law was applied to derive this formula: 

Sum of the Forces=change in momentum/change in time or F=p/t. This means that the net force acting on an object is equal to the change in its momentum divided by the elapsed time. This equation will remain valid regardless of the changes in mass. Another way to denote this relationship is to say that p = Pfinal - Pinitial which equals P=mF*vFinal -mInitial*vInitial. 

 refers to (change in mass/change in time) * velocity. The mass of a rocket changes because its engines release fuel as they are fired up. IF fuel is expelled with the speed v and at the rate change in mass/ change in time, the rocket experiences 

 is defined as the average force exerted by an object times the amount of total time elapsed. Impulse is represented by 

 = Average Force * time. The impulse can be found by 

finding the area underneath a force vs. time graph

. The units for impulse are kg*m/s or N*s, same as momentum. Impulse is a vector and points in the 

. Thus, if we know the impulse or change in momentum delivered on an object and the time interval, we can find the average force that caused the impulse. Always consider the direction of the forces and momentum. The forces that act upon an object affects its change in momentum. 

Make sure you know how to read graphs that relate to impulse, force, and momentum. 

The area of this graph will give you the impulse. 

Momentum and Impulse

When you’re given a two object problem and you’re asked to calculate the change in momentum, take into account the initial momentum and the final momentum individually first of each object. 

. When you solve for the final momentum, decide whether you should use an 

individual mass value or the sum of all masses

If you’re solving for the final velocity of the system, then you should absolutely use the sum of both masses regardless of how many objects there are. 

If an object is initially at rest, it’s initial momentum will be zero since its velocity in the beginning was zero (p = m*v).  

Change in momentum is proportional to the force and time so if you decrease T or F, you decrease the change in momentum. 

You need to be able to interpret different scenarios, 

especially with problems that have multiple external forces acting on the system. When you see problems like that, make sure you find the vector sum of the forces after calculating individual forces. If you’re looking for the momentum, you can either find individual momentums of the objects or find the total momentum of the system. Understand how to apply the formula and make sure you can explain your thought process because some FRQ’s ask for conceptual explanations. 

Representations of Changes in Momentum

 refers to a system that doesn’t lose mass, energy, charge, etc so conserved quantities are considered to be constant. On the other hand, an open system refers to exchanges of energy, charge, etc with the object(s) surroundings. 

 may seem to violate conservation of mass, charge, matter, and energy since the amount of the previously stated quantities can increase or decrease without replacement.  

In terms of momentum of a system, internal forces, like all forces, always occur in action reaction pairs. 

Since the forces in action reaction pairs are equal and opposite due to Newton’s 3rd law, internal forces must always sum to zero. 

If the internal forces cancel, that means that the sum of the total forces must simply be all of the external forces. External forces could sum to zero but that won’t always be the case. 

The change in net momentum is directly related to the net external force. 

If the net external force acting on a system is equal to zero, then its net momentum is conserved so pinitial = pfinal. This only applies to the net momentum of a system

, not individual momenta of each object. 

Open and Closed Systems: Momentum

If the net force acting on an object is zero, then its momentum is conserved. Some forces in one direction may be zero while another direction will have several forces. For example, a ball in free fall would have a net force of zero in the x direction while the y direction’s net force 

is not equal to zero in that specific case. 

Let’s talk about types of collisions and whether momentum is conserved in each collision respectively. A 

refers to a situation in which two objects strike each other and whether they stick together or rebound. The net external force is either zero or negligibly small. Even if momentum is conserved during a collision, the kinetic energy may not be conserved because during the collision, KE can be converted into other forms of energy.

If the initial kinetic energy equals the final kinetic energy, then the objects went through an 

 since KE was conserved and so was momentum. In situations where KE isn’t conserved during a collision due to losses associated with heat, sound, etc, that type is known as an 

inelastic collision (stick together). In either type of collision, momentum will be conserved but the KE may not be so it’s important to be able to identify which collision is occurring in the problem. 

the objects stick together after the collision after colliding. 

Two carts of the same mass lie on a table. The first cart is moving and the second cart is at rest. At the end of the collision, the two carts were stuck together. What is the final speed of the system? 
To find the initial momentum of two carts, do pinitial = m1*v1 + m2*v2. To find the final momentum of two carts that stick together after the collision, do pfinal = (m1 + m2) *vfinal. You can set the initial equation equal to the pfinal equation since momentum is conserved. Finally, solve for the final velocity.

you can also use the Kinetic Energy formula to solve the problems since KE and momentum will be conserved.

so use a similar process to the example and solve for what the question is asking for. The final velocity of the system can be found using KE as well but remember to use the total mass in KE final. 

If the problem is a 2D question, consider both directions separately and then solve for the final KE, Momentum, or velocity. If you aren’t given the net force or the vector sum of the velocity, you may have to use the angle given to solve for those values individually. 

Center of Mass of a system of masses is the point where the system can be balanced in a uniform gravitational field. 

For example, consider a hammer that has a heavy head but less mass in the handle. The center of the mass of the object would be closest to the heaviest side or the head of the hammer. To calculate the center of mass, you can use the formula xcm=m1x1+m2x2+ ...(m1+m2+...) to find the x coordinate for the center of mass. In the equation, x1 is the distance from one end of the object. The same formula can be used for the Y direction. You can manipulate the formula slightly if you have more than two objects by adding m3x3 and more depending on how many objects there are in the system.  

If a system has a net force of zero, then it follows that the acceleration of the center of the mass will be zero. Likewise, if a mass is moving initially, the center of mass will move with the same velocity. 

the center of mass of a system accelerates precisely as if it were a point particle of mass M acted upon by the force Fnet, ext. 

Conservation of Linear Momentum

Free 2020 ACT Test Prep | Video Reviews + Study Tips | Fiveable

Reading

Writing

Math

Science

Essay

First Unit

AP Art History Exam

AP Art History Exam Prep 2020 | Reviews + Free Study Help | Fiveable

AP Art History

Free Reviews

Unit 1: Global Prehistory, 30,000–500 bce

Unit 2: Ancient Mediterranean, 3500 bce–300 ce 

Unit 3: Early Europe and Colonial Americas, 200–1750 ce 

Unit 4: Later Europe and Americas, 1750–1980 ce

Unit 5: Indigenous Americas, 1000 bce–1980 ce 

UNIT 6: Africa, 1100–1980 ce 

UNIT 7: West and Central Asia, 500 bce–1980 ce 

UNIT 8: South, East, and Southeast Asia, 300 bce–1980 ce 

UNIT 9: The Pacific, 700–1980 ce 

UNIT 10: Global Contemporary, 1980 ce to Present

Join our Discord

Unit 5: Momentum

AP Physics 1

all

videos

study guides

slides

browse by units

Free Reviews 2020

AP Physics Essentials

Unit 1: Kinematics

Unit 2: Dynamics

Unit 3: Circular Motion

Unit 4: Energy

Unit 5: Momentum

Unit 6: Simple Harmonic Motion

Unit 7: Torque & Rotational Motion

Unit 8: Electric Charges & Electric Force

Unit 9: DC Circuits

Unit 10: Mechanical Waves & Sound

Free Response Questions (FRQs)

Multiple Choice Questions (MCQs)

Blogs

Join Our Discord

Unit 5: Momentum

AP Physics 1

all

videos

study guides

slides

browse by units

Free Reviews 2020﻿

AP Physics Essentials﻿

Unit 1: Kinematics﻿

Unit 2: Dynamics﻿

Unit 3: Circular Motion﻿

Unit 4: Energy﻿

Unit 5: Momentum﻿

Unit 6: Simple Harmonic Motion﻿

Unit 7: Torque & Rotational Motion﻿

Unit 8: Electric Charges & Electric Force﻿

Unit 9: DC Circuits﻿

Unit 10: Mechanical Waves & Sound﻿

Free Response Questions (FRQs)﻿

Multiple Choice Questions (MCQs)﻿

Blogs﻿

Join Our Discord

Free Reviews 2020

AP Physics Essentials

Unit 1: Kinematics

Unit 2: Dynamics

Unit 3: Circular Motion

Unit 4: Energy

Unit 5: Momentum

Unit 6: Simple Harmonic Motion

Unit 7: Torque & Rotational Motion

Unit 8: Electric Charges & Electric Force

Unit 9: DC Circuits

Unit 10: Mechanical Waves & Sound

Free Response Questions (FRQs)

Multiple Choice Questions (MCQs)

Blogs