[airaws]

Hi my questions are these... help :)


1) Two boxes are placed are placed side by side on a frictionless surface so that they touch each other. Box A has a mass of 4 kg. Box B has a mass of 12 kg. A constant force of 24 N is applied to box A. What force does box A exert on box B?


a) 1.5N [ right] b) 3 N [right] c)6 N [right] d) 24N [left] e)4N [left]


2) A student moves an object a displacement of 2.om [E} with a force of 22N [E]. The force of the fiction is 2.0N. How much work is done on the object?

a) 0 J b) 40 J c) 42 J d) 44 J e) 48 J


3) An adult and a child exert a total force of 588N to push a car 15 m down their driveway. The adult exerts twice as much force as the child. `How much work does the chills do?

a) 1.8 Kilo joules b) 2.9KJ C) 8.8 KJ d) 5.9 KJ e) None of the above


4) a 500 Kg mass is dropped from height of 3.00m. Assume that there is no air resistance. The kinetic energy of the mass just before hitting the ground is :


a) 147 J b) 169 J c) 236 J d) 248 J e) 15 J



5) a Porsche and a Corvette are having a race. The Porsche has a mass of 1275 kg and is traveling at 258 Km/h. The Corvette has a mass of 5100 kg and is traveling at 129 km/h. Which of the following statements regarding the kinetic energy of the two cars is true?


a) K.E. ( Porsche)= K.E. (Corvette)
b) K.E. ( Porsche)= 0.5 K.E. (Corvette)
c) K.E. ( Porsche)= 2.0 K.E. (Corvette)
d) K.E. ( Porsche)= 4.0 K.E. (Corvette)
e) K.E. ( Porsche)= 8.0 K.E. (Corvette)


6) The distance between successive nodes in the vibrating source is 10 cm. the frequency of the source is 309 Hz. What is the wavelength?

a) 20 cm b) 25cm c) 10 cm s) 30 cm e) 5 cm


7) a roller coaster at Wonderland has two vertical loops. The height of the first loop is 20. 5 m above the ground, and the height of the second loop is 18.0 m above the ground. Idf the speed at the top of the first loop is 5.2 m/s, then what is the speed of the roller coaster at the top of the second loop? Assume a frictionless track.

a) 2.7 m/s b) 7.1 m/s c) 7.7 m/s d) 8.7 m/s e) 10.3 m/s


8) Two tuning forks, having frequencies of 310 Hz respectively, are sounded together loudly. An observer standing at a point several meteres away will hear:


a) Continuous silence
b) A sound with 20 beats per second
c) A sound with 10 beats per second
d) A sound with 5 beats per second
e) A sound whose frequency is 315 Hz

[HelpinHere]

I'm not going to give you any answers, but I'll tell you how to find each answer.
If you need any further help with any questions, ask.

1) Two boxes are placed are placed side by side on a frictionless surface so that they touch each other. Box A has a mass of 4 kg. Box B has a mass of 12 kg. A constant force of 24 N is applied to box A. What force does box A exert on box B?

Force is never gained or loss, only changed. From a box one third the size of another box, the force will be reduced by what factor?
The direction depends on which side each box is on.

2) A student moves an object a displacement of 2.0m [E} with a force of 22N [E]. The force of the fiction is 2.0N. How much work is done on the object?

Work = Force x Distance

3) An adult and a child exert a total force of 588N to push a car 15 m down their driveway. The adult exerts twice as much force as the child. `How much work does the chills do?

"chills"?? Do you mean child?
2x (adult) + x (child) = 588
solve for the child.
W = F x D

4) a 500 Kg mass is dropped from height of 3.00m. Assume that there is no air resistance. The kinetic energy of the mass just before hitting the ground is :

Just find Kinetic Energy (Ek)
Ek = .5 m x v^2
Find velocity using acceleration due to gravity (-9.8 m/s)

5) a Porsche and a Corvette are having a race. The Porsche has a mass of 1275 kg and is traveling at 258 Km/h. The Corvette has a mass of 5100 kg and is traveling at 129 km/h. Which of the following statements regarding the kinetic energy of the two cars is true?

Ek = .5 m x v^2
Calculate Ek for each car, then compare.

6) The distance between successive nodes in the vibrating source is 10 cm. the frequency of the source is 309 Hz. What is the wavelength?

Wavelegnth = Speed / Frequency

7) a roller coaster at Wonderland has two vertical loops. The height of the first loop is 20. 5 m above the ground, and the height of the second loop is 18.0 m above the ground. Idf the speed at the top of the first loop is 5.2 m/s, then what is the speed of the roller coaster at the top of the second loop? Assume a frictionless track.

Find velocity by gravity x height (first loop)
Subtract velocity of second loop (gravity x height)

8) Two tuning forks, having frequencies of 310 Hz respectively, are sounded together loudly. An observer standing at a point several meteres away will hear:

"having frequencies of 310 Hz respectively" seems worded incorrectly. Are you sure that this is how it is worded?
With it worded like that, I am unsure as to how to solve this last one...

[Unknown008]

I just wanted to add some things in addition;

1. For that use F=ma (F= force, m=mass, a =acceleration) And keep in mind that energy is not destroyed but converted, like HelinHere said.

2. Here you should know that force will be NET force.

3. Is OK

4. Here also, energy is not destroyed but converted. Use

You'll obtain potential energy, while m = mass, g =acceleration due to gravity, h = height above the ground.

Since at the top, potential energy is maximum and kinetic energy is zero, when the body touches the ground, kinetic energy is maximum while the potential energy is zero.

5. Is OK

6. If you know the formula

where v = velocity (in m/s), f = frequency (in Hz) and = wavelength, you should be able to do it.

7. Well, I don't know about that method from HelpinHere, here's mine, perhaps more lengthy;

Find total energy with the rollercoaster through and in the first loop. Add these two values for energy. (let the mass of the rollercoaster be m)

Find the potential energy in the second loop. Subtract that energy from the first loop's total energy to obtain the kinetic energy it has in the second loop.

Finally, through , you'll have the speed in the second loop.

8. I agree with HelpinHere, there's a little problem of wording...