Q: A hiker climbs a mountain with a vertical elevation gain of 800 m. If the hiker's mass is 70 kg, what is the increase in gravitational potential energy?

$$U_{grav} = 5.49 \times 10^5$\ \mathrm{J}$$

Question 1

A 2.0 kg object is dropped from a height of 5.0 m. Ignoring air resistance, what is the change in gravitational potential energy as it reaches the ground? Use $$g = 9.8\ \mathrm{m/s^2$}.$$

Accepted Answer

$$\Delta U_{grav} = -98\ \mathrm{J}$$

Question 2

Which of the following statements about conservative forces is TRUE?

Accepted Answer

The work done by a conservative force is zero if the starting and ending points are the same.

Question 3

A block attached to an ideal spring (force constant $$k) is $$pulled and released from rest at $$x = A. $$What is the maximum kinetic energy the block will have during its motion?

Accepted Answer

$$\dfrac{1}{2}kA^2$

Question 4

A hiker climbs a mountain with a vertical elevation gain of 800 m. If the hiker's mass is 70 kg, what is the increase in gravitational potential energy?

Accepted Answer

$$U_{grav} = 5.49 	imes 10^5$\ \mathrm{J}$$

Question 5

Which of the following is an example of a nonconservative force?

Accepted Answer

Friction

Question 6

A 0.5 kg ball is thrown vertically upward with an initial speed of $$10\ \mathrm{m/s}. $$What is its maximum height above the launch point? (Ignore air resistance.)

Accepted Answer

$$5.1\ \mathrm{m}$$

Question 7

The elastic potential energy stored in a spring is given by $$U_{el} = \dfrac{1}{2}kx^2$. If a spring with k = 200$$\ \mathrm{N/m}$$ is compressed by 0.10$$\ \mathrm{m}$$, what is the stored energy?

Accepted Answer

$$1.0\ \mathrm{J}$$

Question 8

Which statement best describes the law of conservation of energy?

Accepted Answer

Energy is never created or destroyed; it only changes form.

Question 9

A block slides down a frictionless incline and compresses a spring at the bottom. Which equation correctly expresses the conservation of mechanical energy for this system?

Accepted Answer

$$mgh = \dfrac{1}{2}kx^2$

Question 10

Which of the following is TRUE about the work done by gravity when an object moves along a curved path from height $$h_1 to$$ $$h_2$$?

Accepted Answer

It depends only on the vertical displacement $$(h_2$ - h_1$).$$

Question 11

A spring is stretched by $$0.20\ \mathrm{m}$$ and does $$4.0\ \mathrm{J} of $$work. What is the spring constant $$k$$?

Accepted Answer

$$k = 200\ \mathrm{N/m}$$

Question 12

Which of the following is a property of a conservative force?

Accepted Answer

It can be expressed as the negative gradient of a potential energy function.

Question 13

A car tire heats up after driving due to internal friction. What type of force is responsible for this energy transformation?

Accepted Answer

Nonconservative force

Question 14

For a potential energy function $$U(x)$$, at which point is the force $$F_x$$ zero?

Accepted Answer

Where $$\dfrac{dU}{dx} = 0$$

Question 15

A glider attached to a spring oscillates on an air track. At what position is the elastic potential energy of the spring maximum?

Accepted Answer

At the position of maximum compression or extension

Question 16

Which of the following best describes stable equilibrium in terms of potential energy?

Accepted Answer

A point where $$U(x) is $$minimum and $$F_x = 0$$

Question 17

In three dimensions, the force from a potential energy function $$U(x, y, z) is $$given by:

Accepted Answer

$$\vec{F} = -
abla U$$

Question 18

A gymnast balances on one hand at the top of a vertical pole. What type of equilibrium is this?

Accepted Answer

Unstable equilibrium

Question 19

If a system is acted on only by conservative forces, which of the following is TRUE?

Accepted Answer

The total mechanical energy of the system is conserved.

Chapter 07

Guida di studio - Domande di pratica

Study guide - Flashcard