General physics Flashcards
How to measure the length a wire properly?
1) Wire must be laid straight.
2) Its start must be kept at the ‘0’ point on the ruler.
3) The ruler must be properly calibrated.
How to measure the thickness of a sheet and the time period of one oscillation?
Take the thickness of a large number of sheets (let’s say 500) and divide it by the number of sheets you took (in this case, 500).
Take the time for a number of oscillations (let’s say 20) and divide by the number of oscillations you took (in this case, 20).
How to measure the volume of an irregular shape?
THE DISPLACEMENT METHOD:
1) Fill a measuring cylinder with water enough to submerge the object. Take the volume readings. This will be the initial volume.
2)Immerse the object into the water in the cylinder and take the reading of the volume of water displaced. This will be the final volume.
3) The volume of the object will thus be = final volume - initial volume.
(For an object that floats, use a wooden or steel block.)
What is the volume of a cube, a cuboid, a cylinder and a sphere?
Cube = s³
Cuboid = lwh
Cylinder = πr²h
Sphere = ⁴⁄₃πr³
Density of water?
1000kg/m³ or 1g/cm³
What are some graph characteristics?
st graph:
1) Gradient is speed.
2) Horizontal graph means the object is at rest.
3) Slope increasing represents constant acceleration. Slope decreasing represents constant deceleration.
5) The steeper the slope, more is the constant speed.
vt graph:
1) Gradient is acceleration.
2) Area under the graph is distance.
3) Horizontal graph means constant speed.
4) Slope increasing is increasing acceleration. Slope decreasing is decreasing acceleration.
5) Downwards slope increasing is increasing deceleration. Downwards slope decreasing is decreasing deceleration.
6) The steeper the slope, more is the constant acceleration.
What is ‘F’ in ‘F = ma’ and what is ‘g’ in ‘W = mg’?
‘F’ is the resultant force.
‘g’ is acceleration due to free fall or gravity and its value is 9.8N/kg not 10N/kg.
What does an accelerating object imply and what is the resultant force acting on an object with steady speed?
That it is slowing up or slowing down or that it is changing direction (Velocity is vector).
There is no resultant force acting on an object with steady speed.
Stages during sky diving.
1) Right after the jump, weight pulls the person down with some speed. There is no air resistance, and the person is accelerating.
2) After some time, there is some air resistance acting on the person, but it is less than the person’s weight.
3) Slowly air resistance increases with the speed of motion, until it balances the person’s weight.
4) At this point, the person has attained terminal velocity and has a constant speed.
5) As the parachute opens, there is now a large surface area provided for the air resistance to act on. Due to this, there is a bigger force upwards.
6) This makes the person slow down, thus decreasing the speed of motion.
7) A decrease in the speed of motion decreases air resistance and it again balances out the weight. The person has now attained another terminal velocity at a smaller constant speed to make it safe for them to land.
What is the principle of conservation of momentum?
The total momentum before collision is equal to the total momentum after collision.
Vector answer?
Always give magnitude and direction (angle) from the horizontal.
What is the moment correlation and what are the conditions required for an object in equilibrium?
The lesser the distance from the pivot, more will be the force required.
The principle of moment states that: In equilibrium,
1) Resultant or net forces = 0.
2) Net moments = 0 (anticlockwise moment = clockwise moment).
State the Hooke’s law.
The extension of a spring is directly proportional to the load applied to it, given that the limit of proportionality is not exceeded.
Limit of proportionality is till which limit a force can be applied so that the spring still returns back to its original length.
F = kx
‘k’ is the spring constant (stiffness of a spring).
A higher value of k implies that the spring will extend less when a load is applied to it compared to another spring with a smaller k when the same load is applied to it.
‘x’ is the extension.
‘F’ is the load.
What do we consider the pressure for any object in liquid?
Total pressure for an object in water = atmospheric pressure + pressure by water.
Because pressure is greatest at the greatest depth, a dam is thickest at its base.
Pressure in different shaped containers will be equal if the height of liquid in each is same. Volume and shape of the container do not play any role.
State the principle of conservation of energy.
Energy is neither created nor destroyed. It can only be stored or transferred.
