Work and energy

What are three ways in which simple machine can make the work easier ?

• Changing the direction of the force

• increasing speed

• increasing force

• increase work

How can a lubricant increase the efficiency of a machine?

• by increasing friction

• by reducing friction

• decreasing conversion of mechanical energy into thermal energy

Scientist consider conservation of energy to be a _________.

• theory

• Law

• Hypothesis

At what point on the ball's path is the kinetic energy from the ball's motion the least?

• at the lowest point

• at the Highest point

• at the starting point

Give at least two examples of how different forms of energy can be stored.

• Chemical energy of food & fuels

• Gravitational potential energy of the Earth and the Sun

• Kinetic energy of the moving car

• thermal energy of the heated objects

A book is sliding across a horizontal table slows down and comes to a stop. The book's kinetic energy was converted into what form of energy?

• Chemical energy

• Thermal energy

• sound energy

Mechanical energy is always constant.

• True

• False

Which sequence describes the energy conversion in rubbing of the hand on a cold day?

• chemical potential to kinetic to thermal

• kinetic to thermal to chemical potential

• Thermal to kinetic to chemical potential

_________________ is the ratio of the output force to the input force.

Efficiency of a machine can be equal to or greater than 100%