## Posts tagged Physics Homework Study Help

# Answered: Bikes, angular acceleration...

See answers to these related questions.
http://tutor.leiacademy.org/qa/index.php/91/901-slide-show-slide-13-15
Need to calculate the torque and then use |||tau=I\alpha||. to find ||\alpha||.

# Bikes, angular accelerations, and for...

Two 1 kg wheels with fixed hubs starts from rest and equal magnitude 1 N forces are applied to each. The hub and spokes are virtually massless. In order to impart identical angular accelerations, at which angle (theta) must F1 be applied with respect to horizontal?
This is from the lecture slides. I’m not really sure how to solve this o [...]

# Answered: Parallel Axis Theorem

For any object rotating around its center of mass, you will need to use ||I_{com}||. If the rotational axis is away from the center of mass, you will need to use the parallel Axis theorem to find the momentum of inertia in that situation. In applying the theorem, the M would be the total mass of the object and h would be the distance between [...]

# Answered: Angular speed of two points...

The angular speed describes how much rotational angle (usually in radians) are cover per unit time. Being on the same rotational object, if one point goes around certain angle, e.g., ||2\pi|| for a complete circle, any other points on the same object would also experience an rotation of ||2\pi||. Therefore the angular displacement/velocity/ac [...]

# Parallel Axis Theorem

Can someone give me a good explanation of the Parallel Axis Theorem and when to use it? I’m slightly confused about when to apply this equation. Thanks!

# Angular speed of two points on a circ...

A disk is rotating CCW with an angular speed omega.
Two stickers A and B are fixed to different locations on the disk as shown.
Compare the angular speed of the two stickers A and B.
This problem is from one of the lecture slides. Can someone give me a good explanation of why the angular speeds of A and B are the same, but why the linear spee [...]

# Answered: the questions in PPT

This is all depends on the angular momentum of the block before it is dropped on the disk. In the first two cases, the angular momentum of the block is 0. The path of the block goes through the rotational axis, therefore the momentum would be zero — because ||R_\perp =0||.
So in the first two cases, before and after collision, the total [...]

# Answered: conservation Energy and mom...

(a) the two cars had an inelastic collision (stick together), so the total mechanical energy before and after the collision doesn’t conserve.
(b) momentum is always conserved in a collision as long as there is no external forces applied on the system.
(c) without frictional forces and external forces, the total mechanical energy is co [...]

# Answered: Defining a Coordinate Syste...

You can choose positive to be any direction you want. As long as it is consistently maintained in the problem, it should be fine. So pick the one that is more intuitive to you and be consistent with it.

# Answered: Is hw #10 due for a grade?

It is a review homework, but this one does count for grades.

# Answered: 901 slide show slide 13-15

These are problems concerning calculation of torque. You can find first the component of force that is perpendicular to the R. Then multiply that force component with R to get torque ||\tau=F_\perp R||.
Once have torque, you can use ||\tau_{net}=I\alpha|| to get the angular acceleration.
Here, the moment of inertia of the wheels will be appr [...]

# conservation Energy and momentum?

A boxcar at a rail yard is set into motion at the top of a hump. The car rolls down quietly and without friction onto a straight, level track where it couples with a flatcar of smaller mass, originally at rest, so that the two cars then roll together without friction. Consider the two cars as a system from the moment of release of the boxcar [...]

# Defining a Coordinate System in Torqu...

When choosing which direction of the system will be positive and which will be negative, do we always have to choose the counterclockwise direction to be positive in free body diagrams involving torque(s) applied on pulleys with mass? Will points be taken off on exams if we define the positive direction to be clockwise, if that is w [...]

# Answered: Question regarding directio...

The direction of the force doesn’t have a direct relation with on the direction of velocity. You can have a positive net force while the velocity is positive, negative, and zero; and vice versa. The momentum is always in the same direction of the velocity since ||\vec P=m\vec v||.

# Question regarding direction of force...

Is the force (F) on an object and the velocity of the object (V) and the momentum of the object (P) all in the same direction?

# Answered: Question 3 Quiz Week 9

If you pick downward as positive, then ||v_2|| is negative and ||v_1|| is positive. So your ||\Delta P|| would be negative too — a negative P2 minus a positive P1 gives a total negative ||\Delta P||, which means an upward ||\Delta P||. In this case, d is correct.
In addition, think about the forces the ground applie [...]

# Answered: Is there anyway we can get ...

The example problems in the lecture notes are the best problems to practice. Try them and make sure you can do them without looking at the solutions. You can also imagine how to vary the examples a bit to create new problems to practice.

# Question 3 Quiz Week 9

Question 3 Quiz Week 9
I don’t have the correct answers for this/any quiz.
A basketball of mass m dropped from a certain height hits the ground with a downward speed v(1) and bounces back with an upward speed v(2) leaving the ground. Ignoreair resistance during the process. What is the impulse applied by the ground to the metal ground.
[...]

# Answered: Textbook Page270 Chapter 9

This level of questions won’t be on midterm. Midterm questions will be similar to the examples in my lecture notes and previous quizzes.