Recent content by tonyh

The formula in the previous post is incorrect (that's the magnitude of the *radial* component of the acceleration). What formula are you using for tangential acc?

Hmmm, sounds like a homework problem. You need to think about conservation of momentum and conservation of mechanical energy.

Yes. Provided there is no net external torque the initial angulur momentum will be conserved - in both magnitude and direction.

That is my understanding. Perhaps one of the mentors could comment?

Could you elaborate on this please Russ? Wouldn't this be an internal force? How can an internal force move the centre of mass? There is only one external force on your foot (from the floor). To be balanced, it would require another *external* force wouldn't it?

Just to add a bit to Russ's (correct) answer. Imagine watching the process from the ground outside the car (an inertial frame) in slow motion. You would see the car start to accelerate and move forwards. The bottom half of the body would do likewise, accelerated by forces from the car seat...

You only need to consider the *external* forces. You are pushing against the floor and the reaction to this is a force on you from the floor. So there is net external force on you which propels you forward. I understand this as follows: The car is being 'asked' to partake in circular motion...

The pd (V) across a resistor is set and maintained by the emf source *not* the resistor. Imagine a simple circuit consisting of just an emf source and a resistor (R). A given emf (E) will produce a certain pd (V) across R. The value of R will then determine the current (I). If you increase the...

Displacement is a vector quantity defined as the change in position - from an initial point i to a final point f. Its magnitude is the length of the straight line between i and f and its direction is from i to f. The actual path taken is irrelevant. Distance is a scaler quantity defined as the...

I think you'll need more information that just the initial momentum (P). If you had the time (t) taken for the bullet to come to rest you could treat it as a simple 1-D collision: change in P = average force (F) * t

You can think of this in terms of reducing the momentum (P) of the car to zero. The change in momentum is called Impulse (J) and we can write its magnitude as: J = (average force) F * (time) T. This is derived from Newton's second law in the form F = dP/dt. So for a given J we can reduce...

I don't think so Mayday. A fluid is defined as a substance that cannot withstand a shearing stress, i.e., it starts to flow when subjected to one. This would not apply to a collection of bricks, regardless of how far away you viewed it from.

The fourth state of matter is plasma (ionised gas). And yes, energy can be turned into matter. For example in a process called 'pair production' a gamma ray (high energy photons) transforms into an electron + a positron (mass). The upshot of this mass/energy correspondence is that conservation...

As lzkelley says, this is a projectile question - not a circular motion question. Curvature is to do with the rate of bend of a curve, the rate of turning. And the radius of curvature (at a point) is the reciprocal of the curvature (at that point) - it's a calculus problem. So you need the...

My understanding is that 'harmonic' is synonymous to periodic, and the 'simple' means that the displacement (from the origin) is a sinusodal function of time - i.e., a mathematically simple function. For example x(t)=Acos(wt+\phi), where A,w and \phi are constants. This is equivalent to the...