# Search results

1. ### I Sin x < x

Given that 0 < sin x < x is true for 0 < x < π/2. From the above, can we conclude that 0 < sin (x/2) < x/2? How about 0 < sin (x/5) < x/5? Why? How about 0<sin 3x < 3x ? Why?
2. ### Photoelectric effect

When the emitter is connected to the positive polarity of a battery, it is said that 'Some high speed electrons are still able to reach the collector and therefore there is flow of current.' (1) What is the flow of electrons like in this case? I thought electrons are supposed to flow from...
3. ### Normal force by a spring

Homework Statement A vertical spring is fixed on a table. A book is put on the spring. The book compresses the spring until static equilibrium is reached. Question: Is there a normal force exerted by the spring on the book? Why or why not? Homework Equations The Attempt at a...
4. ### Hooke's law

1. Are the spring forces at both ends of a spring always equal in magnitude? 2. If yes, then the external forces at both ends are also the same in magnitude, aren't they? (Based on Newton's third law) If no, how to find the two different spring forces at each of the end? 3. If the...
5. ### Work-energy theorem

A block (2 kg) is moving with an initial speed of 1 m/s on a horizontal rough table comes to a stop eventually. Applying work-energy theorem to the block-table system, we obtain Change in the kinetic energy of the block + Change in the kinetic energy of the table = Net work done on the...
6. ### Conservation of angular momentum

Homework Statement When a block is dropped to a disc that is rotating with a constant angular velocity about its centre, at the end, we know that both of them will rotate with the same new angular velocity which is slower than the previous one. Question: What is the force that makes the...
7. ### Work done by force acting on a spring

Let say we have a horizontal mass-spring system oscillates without friction on a smooth surface. One side of the spring is attached / fixed to a wall. The other is where the mass is attached to. Let say we choose our system to be the mass and the spring (negligible mass), so our free body...
8. ### Definition of chemical elements

Is oxygen gas a chemical element? Is oxygen atom a chemical element? The oxygen element in the periodic table actually refers to an oxygen atom or oxygen gas that exist naturally in our surrounding air/atmosphere? Thanks to anyone that help and try to explain.