# Need help with my Physics Study Guide!

Discussion in 'Community Discussion' started by TJunkers, Dec 13, 2008.

1. ### TJunkers macrumors 6502a

Joined:
Aug 24, 2007
Location:
New Jersey
#1
So my physics teacher is kinda of a pain in the *** and likes giving "quiz-like" study guides in which we have to answer questions, just so we can study from it! I, unfortunately, am in the middle of moving, and have no time to do this! The test is tomorrow. Please, any help you can give me would be greatly appreciated!

Thanks!

Physics - Study Guide

2. ### LeoFio macrumors regular

Joined:
Jul 30, 2008
Location:
New York
#2
I think the quiz like study guides are a great idea to help you prepare for a test. I'll give you one of the answers: Acceleration is equal to the rate of change of velocity.

The rest are up to you if you want to do well on your test

3. ### TCU macrumors newbie

Joined:
Dec 10, 2008
#3
Your weight and mass are different in that
C) your weight depends upon local gravity but your mass does not.

Cheers.

4. ### KompleX macrumors regular

Joined:
Mar 4, 2008
Location:
Downey, CA
#4
i've never studied physics before, but even an idiot (such as myself ) should know a few things about how nature works.

2. Which of the following devices on a car can be used to cause the car to accelerate?
A) The gas pedal

3. The acceleration of an object is equal to
B) the rate of change of its velocity

15. Astronauts in the space shuttle feel weightless because
B) they are in a constant state of free  fall.

18. What does the period of a pendulum depend on?
C) Length and gravity.

5. ### spazattack674 macrumors regular

Joined:
May 17, 2006
Location:
Boston
#5
1. B, F=ma so if you have F(big car)=2ma and F(small car)=ma, you can neglect the a, making F(big car)=2m and F(small car)=m. So, dividing by 2, one yields F(big car)/2=m, and with substitution, one finds that F(small car)=F(big car)/2, so, the same acceleration is achieved by applying half the force.

2. D, because the brake pedal would yield a negative acceleration, but still, an acceleration. Also, a steering wheel would produce centripetal acceleration, and rather obviously, a gas pedal would cause a change in speed, making an acceleration.

4. A, this is somewhat of a guess, but because there was no force acting on the object, there must have been no movement. So, to someone on the ground, and to the paper, the paper stayed still.

5. D, because it mentions a constant velocity. So, no change in velocity, no acceleration. The rest of the info provided is extraneous.

Ill add more as I become more bored. As far as I know, my answers are correct, but still, I could be wrong.

6. ### Shaun.P macrumors 68000

Joined:
Jul 14, 2003
Location:
Omicron Persei 8
#6
1. B. F = ma. If a is constant, then both separate equations are:

F = 2ma (as one of the cars is twice the mass) and F=ma. Cross multiply to find out a in both cases (i.e. a=f/2m and a=f/m). So same acceleration with half the force.

2. D. Gas can cause an acceleration. The brake can cause a deceleration (negative acceleration). The steering wheel - when changing direction the acceleration would change.

3. B

The acceleration is equal to the rate of change of velocity. i.e. d/dx(v) = a. That is, when you differentiate the velocity, you get acceleration. The derivative is simply the rate of change.

4. It depends. To an observer, the car is moving away. Even if the papers move backwards in the car (which they are), they are still moving away from the observer. So B.

5. D. The rest of the question is filler. The car has constant velocity. It doesn't matter about other forces, if the car is traveling at a constant speed (in a straight line) the acceleration is zero.

6. Work done is Ew = FxD

The resultant force is 10-7 = 3 and the distance is 3m, so 9J. Hmm I'm missing something!

7. Hmm

8. C. Your weight on the moon would be lighter due to the lower gravitational field. Your mass never changes.

9. B. As it accelerates as 2m/s it's velocity increases. So it covers the greater distance during the last second. Don't be fooled by D. It's acceleration is not increasing - it is constant - it's VELOCITY is increasing.

10. A bit misleading. The correct answer is A. It stops accelerating. When you throw something in the air, gravity is taking into account. As you are throwing the item AGAINST gravity, when it is thrown up, its acceleration is -9.8 then it decelerates until the top of its path when its acceleration is 0. When it falls back down it accelerates from 0 to +9.8. You could also say D - the acceleration changes, but that is taking into account the whole movement of the projectile. The question states at the top of it's path.

11. B.

12. No idea.

13. B. If you move to the left on a plane, things will roll to the left. So it can only be B or C. However it can't be C as it says constant velocity. Therefore nothing will be accelerating. The foil ball starts from rest therefore an acceleration must have been present. The only answer could be B.

7. ### spazattack674 macrumors regular

Joined:
May 17, 2006
Location:
Boston
#7
I think it's just looking for them separately, not the resultant force. So it would be w=(10)(3)=30J
and then w=(7)(3)=21J

So, yes, the work that is actually being done is 9J (30-21), but I believe the question is asking for each force separately. Which isn't really "work" because it's not being permanently displaced per se.

7. I want to say B, but that's for the vertical component. It is true that at the top of a path the speed=0.

10. I would have said B for this one. Not exactly sure though, like the above poster commented, the question is misleading.

8. ### Frisco macrumors 68020

Joined:
Sep 24, 2002
Location:
Utopia
#8
It's time for you to take a physics course