Physics Queries?

Question

Answer as many questions as you know. Please give correct explanations.
Q.1 A ladder is resting with one end on a vertical wall & the other on a horizontal floor. Is it more likely to slip near the bottom or near the top?

Q.2 A hollow sphere, a solid sphere, a disc & a ring all having same mass & same radus roll down an inclined plane. If no slipping takes place, which one will take the smallest time to cover a given length?

Q.3 A helicopter flies off, its propellers rotating. Why doesn't the body of the helicopter rotate in the opposite direction?

Q.4 When the angular speed of an object increases, its angular momentum may or may not increase. Give an example of each.

Answer 1

1.) Depends on the geometry and the coeff. of friction.

2.) Ring.

3) Its stabilised by the tail

4) Increases : Dimensions of body remains constant.

Same : Dimensions change.

Answer 2

1. Well, really, they'd both slip at the same time. Or did you mean the placement of the load? The bottom of the ladder will be the end with the most friction on it, therefore the farther away (horizontally) that you get from the bottom, the more likely you are to slip. So the higher you climb, the more dangerous it gets.

2. The solid sphere, because it has the least amount of inertia. This is because most of its mass is concentrated towards the center.

3. It is much heavier (thus has more inertia) than the rotor blades, so their equivalent accelerations are very different. The small rotor on the tail takes care of that little bit of extra torque.

4. If a wheel is spinning and speeds up, its angular momentum will increase. On the other hand, if a figure skater in a spin pulls in her arms and legs close to her body, her angular velocity will increase without a change in angular momentum. This is because the skater's rotational inertia is decreased by moving her mass closer to the axis of rotation. The wheel's inertia stays the same. Angular momentum will only change if energy is being put into or taken out of the system - angular velocity will change if the inertia changes.

Answer 3

1 well,you know the more the distance of the foot of the ladder from the vertical wall more prone it will be to slip by the top.still much depends on the geometry of the lader(centr of gravity).as well as on the coefficient of friction between the material of the ladder and the material of the groud

2 the solid sphere coz,even if they gain the same momentum the distribution of mass of the solid sphere is most suitable for a run down

3 the helicopter is far too big is size(&mass)to allow thw propeller to cammand it,moreover the force needed to ove the propelor is much more then to move the plane body

4 . If a wheel is spinning and speeds up, its angular momentum will increase. On the other hand, if a figure skater in a spin pulls in her arms and legs close to her body, her angular velocity will increase without a change in angular momentum. This is because the skater's rotational inertia is decreased by moving her mass closer to the axis of rotation. The wheel's inertia stays the same. Angular momentum will only change if energy is being put into or taken out of the system - angular velocity will change if the inertia changes.

Answer 4

1. near bottom (gravity)
2. all same (b/c of same mass)
3. my dear you can't apply law of newton over here, rotating propeller creates a low pressure zone over the top and helicopter flies of easily
4. circular motion for increasing momentum, spiral motion for fixed one..

Answer 5

the web stress of the motorcar is 7560 N due north plus 7340 N due south = 7560 N due north minus 7340 N due north = 220N due north. The acceleration is stress / mass = 220N due north/1600 kg = 11/80 N/kg due North or 11/80 m/sec.squaredue North.

Answer 6

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