Exam 7: Work and Energy

In the International System of Units, the unit of energy in base units is

The total mechanical energy of a system

A ball of mass 0.50 kg is pushed against a horizontal spring of negligible mass and force constant of 450 N/m until the spring is compressed a distance of 0.40 m. When the spring is released, the ball travels along a frictionless, horizontal surface to point B, at the bottom of a vertical circular track of radius R = 1.00 m, and continues to move up the track, where the ball experiences an average friction force of 7.00 N. The speed of the ball at the top of the track

A 10-kg toy car moving at 5.0 m/s hits an initially uncompressed horizontal spring with a spring constant of 2.5*10² N/m. Neglecting the mass of the spring, the maximum compression of the spring is

A crate follows a semicircular path of radius 1.0 m. The tangential component of the net force acting on a crate is 10 N, constant in magnitude. The net work done on the crate is

An apple falls to the ground from a tree. During the fall, the work done by the apple is

A heavy suitcase is carried by a porter a sizable horizontal distance. The work done on the suitcase by the porter

A heavy suitcase is carried by a porter down a flight of stairs. The work done on the suitcase by the Earth's gravity is

A force of variable magnitude acting on a crate is represented in a F vs. x graph. The work done by this force on the crate is represented by

A projectile is launched at an angle of 30^o above the horizontal. Neglecting air resistance, the ratio of the kinetic energies at the top of the trajectory and the launching point is

Car A is three times lighter than car B. Car A moves three times faster than car B. The ratio of the kinetic energy of car A to the kinetic energy of car B is

A spring is stretched 10.0 cm when a 0.200-kg mass is hanging at its end. If another 0.200-kg mass is added to the spring, the elastic potential energy of the spring will be

The work-energy theorem is applied to the (frictionless) flight of a projectile (launched from ground level). The following statements are correct except

A box is in contact with a surface that makes an angle of 30^o with the horizontal. An applied horizontal force of 10.0 N allows the box to slide along the surface at a constant speed. When the box has moved 2.0 m along the surface, the work done on it by the normal force is

A flowerpot of mass m, initially at rest, falls a distance h to the ground below. In the absence of air resistance, the graph that best represents the flowerpot's potential gravitational energy as a function of the distance fallen is

Work done on a body can result in changes in all of the following except

A rock, tied at the end of a rope, is swirled at a constant speed in a vertical circle. The net work done on the rock

Consider two crates of different masses, A and B, at the top of two frictionless inclined planes. The mass of crate A is larger than the mass of crate B. Both crates slide down the inclines from the same height where they are at rest. Crate A slides on the plane that makes an angle of 30^o with the horizontal, whereas crate B slides on the plane making an angle of 45^o with the horizontal. Which crate has a larger speed at the bottom of its plane?

A flowerpot of mass m, initially at rest, falls a distance h to the ground below. In the absence of air resistance, the graph that best represents the flowerpot's mechanical energy as a function of the distance fallen is

If the mechanical energy of a body is conserved,