Recent content by horatio89

You're looking for the flow speed in the needle (which differs from the speed in the syringe body), so the diameter should be 0.25mm. Otherwise, it's correct.

dV/dt is rate of volume flow, which is not flow speed (which is in m/s). In a non-viscous fluid, the rate of volume flow must be constant, which is proportional to the flow speed and the area of the flow path. Hence, dV/dt = A1v1 = A2v2 (V = volume, A= area, v = velocity).

fluid flow rate, or dV/dt, which is a product of the velocity and the area, must always be constant for any non-viscous fluid.

That's it. Because initially, both the mass and the heights are the same, the GPE has to be equal. By conservation of energy, GPE = rot. KE + translational KE. Since I is different, rot KE. has to be different (and by extension angular speed), and since the total energy for the two is equal...

Again, no. Conservation of energy states that initial energy = final energy. What form is the initial energy in? What are the final states of energy? Are the total energy for the two objects similar?

No, you see, angular speed is related to the rotational kinetic energy of the object, which are not equal. Now, examine what is similar for these two objects, there's mass and there's the starting height. These two describe a certain physical quantity, what is it?

It would be helpful if you could state the exact meaning of the variables, especially that of I, V and k, though I think I know what they mean... I also have a feeling that k is a constant describing loss of power to the surroundings, but I can't be sure until you provide more info.

Yes, but imagine this, the dog tries to swim at a velocity (and hence a route) perpendicular to the bank, but the stream has a velocity parallel to the bank, pushing it downstream as it swims. Wouldn't it be moving at an angle? I'm sorry if I wasn't clear earlier, for a), your equation is...

a) The first part is on Pascal's Principle. We know that the pressure exerted by the nurse must be equal to the pressure required to push the serum into the blood. (Hint: Do check out what 140 - 100 means, it's very important) b) Fluid flow rate must always be...?

c) What is the condition for the conservation of angular momentum? Does it hold in this case? d) Compare the rotational KE of the system before and after the rod is placed on the turntable.

2nd paper Q5: The amount of rotational KE an object has depends on the object's moment of inertia, hence that cannot be an answer. (Hint: Think conservation of energy, what is always the same of two objects of the same mass going down the same height?) Otherwise, well done!

To determine the direction of friction, it is worth recalling that friction always acts in the opposite direction of the motion of the object. In which direction is the block "trying" to move? Also, the block is stationary: what does this tell you about the magnitude of friction?

It would help if you draw the free body diagram for the forces acting on the pendulum at the equil. point, and the two maximum points. It is worth remembering though, that a pendulum is moving is a circular motion, and there must be a net centripetal force (which is a resultant force, and...

Not really, we are treating the bob as having the moment of inertia of a single point particle rotating about an axis

a) Velocity = displacement/time, therefore, time = ?. To find velocity, simply add the velocity of the stream and the dog. (Note: Recall that velocity is a vector). For this part, we are interested in the component of velocity perpendicular to the bank. b) Well, from a), you'll realize that...