Recent content by rdt2

Think of the motion of a car. The independent variable is time t, but to describe its path you have to give its (initial) position _and_ its (initial) velocity, the derivative of position.

The 'Calorie' commonly quoted in a food context is actually a kilocalorie.

http://en.wikipedia.org/wiki/Orthographic_projection explains the how and why of the projection systems. The 'truncated cone' universal symbol illustrates the difference and the link to Limerick Uni's site is useful. Neither 1st nor 3rd angle is intrinsically superior. UK practice varies...

The geographical variations in bows are interesting. Esssentially, the recurve bow requires a composite material that's good in compression on one side (often made of bone) and good in tension on the other side (often made of leather). In a cool, wet climate, such as the U.K, that's not a...

Strength is (loosely) the maximum force the component can take; toughness is the energy needed to make it fail. Examples: engineering ceramics are brittle, i.e they can't sustain much plastic deformation before they fracture. They have high strength but low toughness. They can take...

Yes - the thinking time is assumed constant, so the thinking distance is linear.

Current thoughts on where nuclear reactors are going are summarised at http://en.wikipedia.org/wiki/Generation_IV_reactor . Obviously, environmental impact is one factor in this but not the only one.

A second spring in series won't make a difference, even if it has a different stiffness. I assume you mean 'stretch' rather than 'compress'? If so, it's most likely that the first spring has been stretched beyond the point where its response is linear. I'm surprised that it didn't hasn't...

Linear algebra is often just another name for matrix algebra.

I introduce tensors starting from something that students already know. For example, in elementary mechanics, it's said that: a scalar is a quantity with a magnitude but no direction (such as temperature). a vector is a quantity with a magnitude and an associated direction (such as...

I introduce the tensor product to show that the dot product and the cross product of two vectors aren't arbitrary definitions but are linked. The tensor product of vector u_{i} and vector v_{j} is the (second order) tensor u_{i}v_{j}. Operating on this with the Kronecker delta \delta_{ij}...

I put this question in the 'Calculus' forum but didn't really get a response. Maybe it's a silly question but I thought I'd try here anyway: Older textbooks on the Calculus of Variations seem to define the first variation of a functional \Pi as: \delta \Pi = \Pi(f + \delta f) - \Pi...

Older textbooks on the Calculus of Variations seem to define the first variation of a functional \Pi as: \delta \Pi = \Pi(f + \delta f) - \Pi (f) which looks analogous to: \delta f = \frac {df} {dx} \delta x = lim_{\delta x \rightarrow 0} (f(x+ \delta x) -f(x)) from...

It does for ferrous metals. I think the simplest explanation is that it's easier to keep dislocations moving (at the 'lower yield stress') than it is to start them moving (at the 'upper yield stress'). Like the difference between static and dynamic friction coefficients. See...

The author is perfectly correct. Here's what I tell my students: "To explain these apparent forces, consider Figure 27.8.3.a, which tracks a particle moving at a constant velocity with respect to an observer in a fixed basis. The time-displacement graph is a straight line. If the...