Fourth year of secondary education
Work, power and energy
I. Sevila
 W.P.E. 
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1.Mark the actions in which work is being done
Carrying a rucksack to school
a vehichle warming up its motor
a computer running a program

2.Choose the statement that lists all the magnitudes that the work done by a force depends on
The force and the speed
The displacement and the direction of the force
The trajectory, the displacement and the time taken
The magnitude and direction of the force, and the displacement
3. The work done to move an object 5.1 m with a 1.4 N force in the direction of the movement is: (you may wish to use the visual )

approximately 2 J
approximately 7 J.
approximately 7 N.

4. The kinetic and potential energies of a 6 Kg object freely falling at 5 m/s from a height of 2 m is:
Potential energy: 75 J, Kinetic energ: 100 J
Kinetic energy: 75 J, Potential energy: 75 J.
Kinetic energy:75 J, Potential energy: 117.6 J.
10. Energy is a physical magnitude that describes the capacity of an object to do work.
True
False
Percentage of questions answered correctly
5. If we drop a 7.5 Kg object from a height of 3 m onto a lever in such a way that it launches a 5.5 kg. object on the other side upwards, would this object be able to reach a height of 4m? You might want to use the visual .
The second object will reach the height because it is lighter than the first one
It won´t reach the height
It will reach the height because its potential energy at the height of 4m will be produced by the kinetic energy of the first object in its collision with the lever.
It won´t reach the height because the mechanical energy of the second object will never be equal to the energy transmitted by the first object when it collides with the lever.
6. In a movement, some or all of the following types of energy and work are involved:
Mechanical and kinetic energies
potential energy and the work done by the force that moves the body
Kinetic energy, potential energy, work done by forces excluding the body´s weight and work lost through fricition
Kinetic energy, potential energy and work done by the body´s weight.
7. The power of a hoist is defined as:
The work done in a unit of time. The SI unit for power is the Watt.
It is the potential energy given to the object that is being lifted. Its SI unit is the Joule.
The speed at which it lifts objects. Its SI unit is m/s.
8. The mechanical energy of a freely falling object is the difference between its potential energy and its kinetic energy.
True
False
9. To lift an object of 100 kg. at a speed of 6 m/s to a height of 4 m, the power of the machine must be at least 5.9 Kw and the work done by the crane is 3.9 kJ.

True
False

Work (W)
What is work (W) in science?
Forces do work
The force of friction and work
Energy
Kinetic energy
Potential energy
The principle of the conservation of energy
Transformation of energy
Work and energy
The power (P) of a force/machine
EVALUATION