Work, Energy an...

The scalar product of two vectors A and B is

Mass and energy are equivalent and are related by

A railway porter is holding a weight of 100 kgs on his head and is standing still. What is the work done by him?

A person trying to lose weight (dieter) lifts a 10 kg mass, one thousand times, to a height of 0.5 m each time. Assume that the potential energy lost each time she lowers the mass is dissipated. How much work does she do against the gravitational force?

A12-pack of Omni-Cola (mass 4.30 kg) is initially at rest on a horizontal floor. It is then pushed in a straight line for 1.20 m by a trained dog that exerts a horizontal force with magnitude 36.0 N. Use the work–energy theorem to find the final speed of the 12-pack if there is no friction between the 12-pack and the floor

The work done by the force is defined to be

Power is defined as

A weight of 20kg falls from a height of 10 m. The work done by the gravitational force is (Take g = 10 mms^-2)

S.I unit of power is

In which case is the work done zero?

Which of the following laws used to solve problems in collisions?

A pump on the ground floor of a building can pump up water to fill a tank of volume 30 m³ in 15 min. If the tank is 40 m above the ground, and the efficiency of the pump is 30%,  how much electric power is consumed by the pump?

The S.I unit of force is

In an elastic collision

Work-energy theorem does not give information on

In an inelastic collision

Physically, the notion of potential energy is applicable only to

In a completely inelastic collision

A bolt of mass 0.3 kg falls from the ceiling of an elevator moving down with an uniform speed of 7 m/s. It hits the floor of the elevator (length of the elevator = 3 m) and does not rebound. What is the heat produced by the impact?

The work done by a conservative force

In which of the following cases is the work done positive?

The total mechanical energy of a system is conserved if the

The casing of a rocket in flight burns up due to friction. At whose expense is the heat energy required for burning obtained?

A tandem (two-person) bicycle team must overcome a force of 165 N to maintain a speed of 9.00 m/s. Find the power required per rider, assuming that each contributes equally.

For a ball dropped from a tower of height h the total mechanical energy is

A trolley of mass 200 kg moves with a uniform speed of 36 km/h on a frictionless track. A child of mass 20 kg runs on the trolley from one end to the other (10 m away) with a speed of 4 ms⁻¹ relative to the trolley in a direction opposite to the its motion, and jumps out of the trolley. How much has the trolley moved from the time the child begins to run?

A 50.0-kg marathon runner runs up the stairs to the top of a 443-m-tall Tower. To lift herself to the top in 15.0 minutes, what must be her average power output?

In which of the following cases is the work done positive?

The launching mechanism of a toy gun consists of a spring of unknown spring constant. When the spring is compressed 0.120 m, the gun, when fired vertically, is able to launch a 35.0-g projectile to a maximum height of 20.0 m above the position of the projectile before firing. Neglecting all resistive forces, determine the spring constant.

If F is a force and d is the displacement in the direction of force then the work done by the force is given by