Project MCQ reviews

GENERAL TIPS FOR ALL UNITS

READ ALL THE QUESTIONS CAREFULLY

SOH CAH TOA carefully

be careful when asked to compare something in terms of the original value, I got the right answer just inversed, for ex: 1/root 2 instead of just root 2, make sure to set ur ratio with the OG and new equation 1st, also i did 3w instead of w/3

always check if a graph will need an x int or not, not all of them start at 0

Unit 1

a block will accelerate when sliding down a ramp, meaning the d v.s t graph will not be linear it will be exponential (the acceleration down the ramp is g sin 0)

when 2 observers are measuring an objects acceleration, they will always have the same measurement if they have the same acceleration (for example a person standing still and a person moving with constant velocity have the same acceleration)

to find when an object is changing directions, use the first kinematic equation and set vf to 0 and solve for time (this works bc when it changes directions it will be 0 for 1 instance)

when given a range of accelerations to help predict a range for the position of an object, plug both accelerations into a kinematic equation and solve for distance to find the min and max distance

When comparing final velocitys of objects thrown in the air, you need to compare the vertical time in air, the shorter component will be slower

Be careful when solving for problems with relative velocities, always try to match what the speed is relative to and solve with said correct values

Unit 2

when given the density of planets and asked to compare the force of gravity, the mass will be related to the radius of the planet³

when trying to figure out where Force of gravity will be 0 between 2 objects with different masses, the location where it is 0 will be closer to the object with less mass

Velocity does not affect forces

uniform circular motion still accelerates since the velocity changes directions

Static friction adapts to any force value that is less then the maximum force needed to keep an object at rest

hookes law F = kx, make sure you use that for spring questions that need to use newtons 2nd law, this is vital for questions asking for spring length / displacement

the tension at the top of a rope will be greater then the middle of the rope

objects cannot exert forces on themselves to influence their motion (newtons 3rd law questions)

pay attention to what object is causing the acceleration and what the answer choices put for their force equations

a blocks weight and an applied force will not create the same acceleration for a pulley system, the one with a blocks weight will have less acceleration due to the mass

Unit 4

the velocity time graph of a ball bouncing elastically will not cross 0 but instead will instantly go negative

be mindful of who is and isnt included in a system / equation when trying to compare values / see the change in a certain value especially for energy

blocks with equal masses will move the same direction as the one already in motion (if 1 is at rest and the other is moving)

when it asks for the momentum at time 40 seconds you will use the instantaneous velocity not the average velocity

an object with less mass will go the opposite direction after an eclectic collision with an object with a greater mass

if there is no force in a system, there is no impulse, no impulse means there’s no change in velocity

0 energy is lost only in perfectly elastic collisions

Unit 5

weight force always acts in the middle, so when asked for torque its almost always ½ L (SUPER IMPORTANT)

when asked for the number of forces, be sure to include all tension, sometimes when making equations tension will get canceled out, be careful

linear acceleration and velocity are both inversely proportional to radius

always look for the phrase constant velocity when asked for net force / torque, if its not constant then it actually has a value

rotational inertia is proportional to the distance from the axis

look into the parallel axis theorem

I = Icm + md² (Icm is inertia about the center and d is distance between center of mass and axis of rotation)

0 = s/R

Unit 6

for questions that ask for what data is required to solve for a certain variable always think of ALL equations with said variable and make a known and unknown chart

friction between 2 objects will decrease angular momentum because the friction is a torque

when asked about the magnitude of an angular quantity, you need to think in clockwise and counter clockwise not Up right and left down for positive and negative

an object moving closer towards the center of a rotating disk will increase angular speed and lower the intertia of the system

escape speed = root 2 G M / r (review uniform circular motion for the derivation)

finding angular momentum on torque time graph - area under the curve then add it to the initial momentum

speed during orbit = root GM/r

change in rotational kinetic energy is equal to the work done by the net torque (VERY IMPORTANT)

^^ compare 2 energies you would need to solve for the work twice using the equation W = torque * change in theta → rF0

Same net force same displacement same radius, nothing but the rotational inertia changed meaning the change in kinetic energy is equal

Unit 7

increasing the mass of an object in a pendulum will not affect the speed but will affect the maximum energy

when trying to get an equation for the graph pay close attention to if the x or y axis have been squared or changed in any other way from an equation it was derived from for ex: period ² will get rid of the square root for the period of a pendulum equation

the amplitude is only ¼ of a full oscillation

the amplitude does not affect the spring constant

review Sin and Cos graphs and functions