A 11.7kg weather rocket generates a thrust of 200N . The rocket, pointing upward, is clamped to the top of a vertical spring. The bottom of the spring, whose spring constant is 550N/m , is anchored to the ground.

A) Initially, before the engine is ignited, the rocket sits at rest on top of the spring. How much is the spring compressed?

B)After the engine is ignited, what is the rocket's speed when the spring has stretched 32.0cm ?

C)For comparison, what would be the rocket's speed after traveling this distance if it weren't attached to the spring?

A stick is resting on a concrete step with 1/7 of its length hanging over the edge. A single ladybug lands on the end of the stick hanging over the edge, and the stick begins to tip. A moment later, a second, identical ladybug lands on the other end of the stick, which results in the stick coming momentarily to rest 46.5° from the horizontal. If the mass of each bug is 3.43 times the mass of the stick and the stick is 16.3 cm long, what is the magnitude of the angular acceleration of the stick at the instant shown?

In a game of basketball, a forward makes a bounce pass to the center. The ball is thrown with an initial speed of 4.9 m/s at an angle of 20 ∘   above the horizontal. It is released 0.80 m above the floor.

What horizontal distance does the ball cover before bouncing?

Describe the differences between circular motions and elliptical motions. Explain how Newton’s universal gravitational law can be applied to study the interplanetary motions.

A proton is trapped in an infinitely deep square well of width L = 5 × 10^-6 nm. This is approximately the size of an atomic nucleus. (It depends on atomic weight.) The proton's mc² = 9.3827 × 10⁸ eV. Note: Atomic nuclei are really spheres. For simplicity, we are treating them as 1-D square wells, which yields the correct order of magnitude result.

1) What is the ground state energy of the proton in this well in eV? E₁ =

2) If the proton is in an excited state, it can fall to a lower energy state and emit a photon (just like an electron does). Suppose the photon's energy is 4.0959 × 10⁷ eV.

Note: This photon is a gamma ray, common in nuclear transitions. What was the proton's initial energy level (i.e., the n value)? n =

3) Suppose an electron were trapped in this well (infinitely deep, with the same width, L). What is the electron's ground state energy in this well in eV? E₁ =

A 6.000 g bullet Is fired with a velocity of 600.0 m/s towards a 2.000 kg stationary target. The target has frictionless wheels and rest on a horizontal surface. When the bullet hits the target, it becomes lodged in it, and the target and bullet move forward at a common velocity. Find the velocity of the bullet and target combination after the collision.

Block A (0.40 kg) and block B (0.30 kg) are on a frictionless table. Spring 1 connects block A to a frictionless peg at 0 and spring 2 connects block A and block B. When the blocks are in uniform circular motion about 0, the springs have lengths of 0.60 m and 0.40 m, as shown. The springs are ideal and massless, and the linear speed of block B is 2.0 m/s. If the spring constant of spring 1 is equal to 30 N/m, the unstretched length of spring 1 is closest to?

For example, Einstein postulated that the speed of light, c, is constant in all inertial frames of reference.

Bohr postulated that electrons go around the atom in orbits and that there are pre-defined orbits, and that moving from a higher orbit to a lower orbit makes releases energy.

I bet there are many other postulates that we take for granted.

Therefore I've a question, how can we claim something violates some physical law, when so many physical laws have been postulated?

All it takes is to disprove one of the postulates and suddenly a lot of things break down because of the claims that are based on the postulates.

True/False please

1. The magnetic field is always conservative

2. Gauss'law for magnetism reflects the fact that there are no electric monopoles.

3. An electrically charged rod will attract a piece of magnetic material.

4. In an AC circuit, the complex power S represents the power supplied to the capacitors and inductors.

5. The capacitance of a parallel plate capacitor increases when a piece of dielectric material is inserted between the plates.

6. If an AC circuit has tow sources with different frequencies, we can add the solutions for each source in phasor space.

7. The ultimate source of all electromagnetic phenomena is electric charges in motion.

8. In an AC circuit, the average power supplied to a resistor is zero.

9. The magnetic field cannot ever do any work.

10. The instantaneous power supplied to any circuit element is always p(t) = i(t)v(t)

11. Both the voltage and current for an inductor must be continuous in time.

12. The relative permeability of a ferromagnetic substance is <1

Thank you!

How conservation laws are tested experimentally independently from each other? what do I mean by that question?

It seems that to test one conservation law experimentally, such as conservation of energy, we will have to assume other conservation laws are correct such as conservation of charge and conservation of momentum and angular momentum...etc.

But to really test any conservation law one has to check if one of them is valid independent from any other one. Is this possible experimentally? if not then how scientists check conservation laws?

The driver of a 1350 kg car, initially traveling at 10.1 m/s, applies the brakes, bringing the car to rest in a distance of 22.0 m.

(a) Find the net work done on the car.

(b) Find the magnitude and direction of the force that does this work. (Assume this force is constant.)

magnitude,direction

You have probably seen people jogging in extremely hot weather and wondered "Why?" As we shall see, there are good reasons not to do this! When jogging strenuously, an average runner of mass 68.0 kg and surface area 1.85 m2 produces energy at a rate of up to 1330 W , 80.0 % of which is converted to heat. The jogger radiates heat, but actually absorbs more from the hot air than he radiates away. At such high levels of activity, the skin's temperature can be elevated to around 33.0 ∘C instead of the usual 30.0 ∘C. (We shall neglect conduction, which would bring even more heat into his body.) The only way for the body to get rid of this extra heat is by evaporating water (sweating).

A: How much heat per second is produced just by the act of jogging? (J/s)

B: How much net heat per second does the runner gain just from radiation if the air temperature is 40.0 ∘C (104 ∘F)? (Remember that he radiates out, but the environment radiates back in.) (W)

C: What is the total amount of excess heat this runner's body must get rid of per second? (J/s)

D: How much water must the jogger's body evaporate every minute due to his activity? The heat of vaporization of water at body temperature is 2.42×10⁶ J/kg . (g)

E: How many 750 mL bottles of water must he drink after (or preferably before!) jogging for a half hour? Recall that a liter of water has a mass of 1.00 kg .

a) A car is driven along a curve at a speed of 38 m/s. If the car

What is a matter Entropy?