Work and Power
Introduction to machines
Simple Machines
Introduction to Energy
Potential and Kinetic Energy
Energy Transformations
100
Which is occurring when work is being done?
Energy is being transferred.
100
What is the mechanical advantage of a pulley?
1.0
100
Which simple machine is best used to split apart an object?
a wedge
100
What is the source of almost all energy on Earth?
The Sun
100
Which set of terms best defines what affects kinetic energy and potential energy, respectively?
velocity, height
100
When a person strikes and lights a match, potential energy in the match is transformed into which types of energy?
Thermal and Radiant
200
A machine has an efficiency of 80%. How much work must be done on the machine so to make it do 50,000 J of output work?
62,500 J
200
Which statement describes how a machine can help make work easier?
It can put out more force than the input force by decreasing the distance over which force is applied.
200
Keisha is making a diagram of a simple machine in the body. Which labels complete the diagram?
X: load
Y: fulcrum
Z: lever
200
As a person pushes a box across a floor, the energy from the person’s moving arm is transferred to the box, and the box and the floor become warm. During this process, what happens to energy?
It is conserved
200
Seema knows the mass of a basketball. What other information is needed to find the ball’s potential energy?
acceleration due to gravity and the height the ball reaches
200
What type of energy transformations occur when energy from the wind is used to generate Electricity
kinetic energy transformed to mechanical energy
300
What is needed for work to be done?
A force must cause an object to move along the same direction as the force.
300
Which refers to the ratio of output force to input force of a machine?
mechanical advantage
300
A wheelbarrow can be used to help lift a load, such as a pile of dirt, and then push the load across a distance.
a wheel and axle and a lever
300
What is the unit of measure for energy?
joules
300
If the kinetic and potential energy in a system are equal, then the potential energy increases. What happens as a result?
Energy of motion decreases.
300
When a spring is compressed, the energy changes from kinetic to potential. Which best describes what is causing this change?
work
400
Adita lifts a book from the floor, carries it across the room, and places it on a high shelf. When is Adita doing work on the book?
She does work as she picks up the book and as she lifts it to the shelf.
400
Which is a result of using a machine?
The distance through which a force acts increases, and the force decreases.
400
How does using a ramp make work easier when loading a piano onto a truck three feet above the ground?
It allows a smaller force to be applied over a longer distance.
400
Which term refers to the ability to do work?
Energy
400
Which two types of potential energies would be types of mechanical energies?
elastic and gravitational
400
When Javier touches a hot mug of tea, energy is transferred from the surface of the mug to his hand. What kind of energy is this?
thermal
500
Which term is the product of force and distance?
work
500
Bill does 1500 J of work on a lever, which is a simple machine. The lever does 1350 J of work on a stone.
What is the efficiency of the lever?
90%
500
Which change would increase the mechanical advantage of dentures, which are artificial teeth?
an increase in the length of the sloped side of the teeth and a constant width of the teeth
500
On a test, Helena is defining energy. Which must she include in order to get her answer marked correct?
the ability to do work
500
What is the potential energy of a 25 kg bicycle resting at the top of a hill 3 m high? (Formula: PE = mgh)
735 J
500
Which activity directly converts energy from the Sun into chemical energy?
Photosynthesis: Example-- a bean plant making its own food to grow
600
A powered winch is used to pull a sailboat to shore. The winch uses a 900 W motor.
If the motor is used for 30 s, how much work does it do? (Power: P = W/t)
27,000 J
600
A machine has a mechanical advantage of 5. What force should be applied to the machine to make it apply 3000 N to an object?
600 N
600
Which simple machine turns about a fixed point called a fulcrum?
a lever
600
How does work affect energy between objects so it can cause a change in the form of energy?
Work transfers energy.
600
What is the value of gravity?
9.8
600
What happens in terms of energy when a moving car hits a parked car, causing the parked car to move?
The moving car transfers kinetic energy to the parked car.