Thomas is given a set of problems for an assignment relating to his interests. A

Question

Thomas is given a set of problems for an assignment relating to his interests. Answer the following two-part question: 1a. A skater can increase her or his angular velocity in a spin by moving his or her arms and legs as far away from the rotation axis as possible. moving her or his arms and legs as close to the rotation axis as possible. moving their center of mass closer to the ice. the skater cannot change his or her angular velocity. Two construction workers must each push a crate up a ramp against the force of gravity and the force of friction. The first worker pushes his crate directly up, while the second pushes his along a zigzag path, which is twice as long as the path of the first worker. The second worker did twice as much work against gravity and twice as much work against friction as the first worker. twice as much work against gravity and the same amount of work against friction as the first worker. the same amount of work against gravity and twice as much work against friction as the first worker. the same amount of work against gravity and the same amount of work against friction as the first worker.

Explanation / Answer

1a.

According to conservation of angular momentum,  (r × mv) is a conserved quantity.

So, if the skater moves his or her arms and legs closer to the rotation axis, r will be decreased which will result in the increase of angular velocity to conserve the angular momentum.

Option B is the correct answer.

1b.

Gravitational force is a conservative force whereas frictional force is not.

We know that the work done under a conservative force depends on the states whereas the work done under other forces depends on the path.

As, the initial and the final points are same by the both paths, work done against gravitational force (Conservative force) by the second worker is same as that of the work done by the first worker.

But, the work done against the frictional force (Non-Conservative force) by the second worker will be twice as that of the work by the first worker.

Therefore, Option C is the correct answer.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.