Exam 8: Potential Energy and Conservation of Energy

The potential energy of a 0.20-kg particle moving along the x axis is given by U(x) =(8.0J/m²)x² + (2.0J/m⁴)x^4. When the particle is at x = 1.0 m its magnituede of its acceleration is:

A 0.75-kg block slides on a rough horizontal table top. Just before it hits a horizontal ideal spring its speed is 3.5 m/s. It compresses the spring 5.7 cm before coming to rest. If the spring constant is 1200 N/m, the thermal energy of the block and the table top must have:

The first graph shows the potential energy U(x) for a particle moving on the x axis. Which of the following five graphs correctly gives the force F exerted on the particle?

A 0.50-kg block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal frictionless surface. The total mechanical energy is 0.12 J. The greatest extension of the spring from its equilibrium length is:

A 25-g ball is released from rest 80 m above the surface of the Earth. During the fall the total thermal energy of the ball and air increases by15 J. Just before it hits the surface its speed is

No kinetic energy is possessed by:

A 5-kg projectile is fired over level ground with a velocity of 200 m/s at an angle of 25 ° above the horizontal. Just before it hits the ground its speed is 150 m/s. Over the entire trip the change in the thermal energy of the projectile and air is:

A block slides across a rough horizontal table top. The work done by friction changes:

A ball is held at a height H above a floor. It is then released and falls to the floor. If air resistance can be ignored, which of the five graphs below correctly gives the mechanical energy E of the Earth-ball system as a function of the altitude y of the ball?

For a block of mass m to slide without friction up the rise of height h shown, it must have a minimum initial kinetic energy of:

An elevator is rising at constant speed. Consider the following statements: I. the upward cable force is constant II. the kinetic energy of the elevator is constant III. the gravitational potential energy of the Earth-elevator system is constant IV. the acceleration of the elevator is zero V. the mechanical energy of the Earth-elevator system is constant

A particle moves along the x axis under the influence of a stationary object. The net force on the particle, which is conservative, is given by F = (8N/m³)x³. If the potential energy is taken to be zero for x = 0 then the potential energy is given by:

A force on a particle is conservative if:

A body at rest in a system is capable of doing work if:

A 2.2-kg block starts from rest on a rough inclined plane that makes an angle of 25 ° with the horizontal. The coefficient of kinetic friction is 0.25. As the block goes 2.0 m down the plane, the mechanical energy of the Earth-block system changes by:

A 2-kg block is thrown upward from a point 20 m above the Earth's surface. At what height above Earth's surface will the gravitational potential energy of the Earth-block system have increased by 500 J?

A small object of mass m starts at rest at the position shown and slides along the frictionless loop-the-loop track of radius R. What is the smallest value of y such that the object will slide without losing contact with the track?

A ball of mass m, at one end of a string of length L, rotates in a vertical circle just fast enough to prevent the string from going slack at the top of the circle. The speed of the ball at the bottom of the circle is:

An ideal spring is used to fire a 15.0-g block horizontally. The spring has a spring constant of 20 N/m and is initially compressed by 7.0 cm. The kinetic energy of the pellet as it leaves the spring is:

Which one of the following five quantities CANNOT be used as a unit of potential energy?