Question

Please explain and show the solution

Q6: Statics

It’s the middle of winter and the ground around and walls of your house are covered in a particularly slippery ice. You need to climb a ladder so rest it at a 45 degree angle against the house. It would slip instantly except that you have some high friction (big µ) pads. Unfortunately you only have pads for one side of the ladder – either against the ground or against the wall. Where should you put them to most safely climb the ladder?

A. It doesn’t matter – placing the pads on either side will have the same effect

B. Both might work, but the ground is better

C. Both might work, but the wall is better

D. Only the ground will work

E. Only the wall will work

Q7 Conservation of Angular Momentum/Rotational Kinetic Energy:

Changing I Consider a cylindrical toy which can switch from having its mass roughly equally distributed across its cross-section (solid cylinder) to having its mass concentrated at its outer edge (hollow cylinder). With the toy spinning on frictionless bearings around its central symmetry axis, you push a button and it converts from “solid” to “hollow” mode. What happens to its rotational kinetic energy?

A. Increases by a factor of 4

B. Increases by a factor of 2

C. Stays the same

D. Decreases by a factor of 2

E. Decreases by a factor of 4

Q8 Center of mass

A man sits in the back of a small boat in still water. He then moves forward to the front of the boat and sits there. Afterwards the boat:

A. is forward of its original position and moving forward.

B. is forward of its original position and moving backward.

C. is forward of its original position and not moving.

D. is behind its original position and moving backward.

E. is behind its original position and not moving.

Answer 1

Q 6 . Ladder has always requirment to more downward friction because amount of effort at downward is less in oppsoite to friction , so we get more advantage of friction there . on the side of wall as we know that direction of applied force is downward , surface has to apply friction in upward, now if you applly pad on wall side it will also has some mass and gravitaionl pull on it toward down which will oppose friction.

So option b) is correct that both will work but ground is better.

Q7 ) As we know that Rotational kinetic energy = 1/2 I ²   , Here I is moment of Inertia and omega is angular velocity.

Hollow has MI = MR² and Solid has MR²/2

So once solid is converted into Hollow ==> Energy becomes double.

SO option B) is Correct.

Q8 )

Once person will move toward front , center of mass will change, com will shifted towards front.

SO Boat will shift little Backward, it will not move constantly will slightly shifted to backward from original place.