CH5

Question 1

Define Work Done

Answer 1

Product of the force and distance moved in the direction of the force

Question 2

What is the formula for work?

Answer 2

W = F * x
where: F is the force and x is the direction moved in the distance of the force

Question 3

What is meant by work?

Answer 3

Work is the amount of energy transferred when an external force causes an object to move over a certain distance

Question 4

What is the unit of Work?

Answer 4

Jules or Nm. 1J=1Nm

Question 5

How is work done calculated when the force is applied at an angle to the direction at which the object moves?

Answer 5

W = (F cos theta) * x

where theta is the angle between F and the direction of motion

Question 6

What is meant by energy?

Answer 6

Energy is the capacity of doing work

Question 7

Is energy scalar or vector?

Answer 7

Scalar qty

Question 8

What is the SI unit for energy

Answer 8

Joule

Question 9

What is kinetic energy? Examples?

Answer 9

energy due to movement of objects with mass.
Examples: moving car, moving atoms

Question 10

What is Gravitational potential energy? Examples?

Answer 10

energy due to the position of an object in the Earth’s gravitational field
Examples: child at top of a slide, water held in clouds

Question 11

What is meant by “potential” in physics?

Answer 11

It is often used to mean “hidden” or “stored”

Question 12

What is chemical energy? Examples?

Answer 12

Energy contained within the chemical bonds between atoms. It can be released when the atoms are rearranged.
Examples: energy stored in a chemical cell, energy stored in petrol and released when it burns

Question 13

What is elastic potential energy? Examples?

Answer 13

energy stored in an object as a result of reversible change in shape.
Examples: a squashed spring, a stretched guitar spring

Question 14

what is electrical potential energy? Examples?

Answer 14

Energy of electrical charges due to their position in an electric field.
Examples: static energy on a charged balloon, electrical charges on a thundercloud

Question 15

What is nuclear energy? Examples?

Answer 15

Energy within the nuclei of atoms - it can be released when the particles with the nucleus are rearranged.
Examples: energy from fusion processes in the Sun, energy from nuclear fission reactors

Question 16

What is radiant (or electromagnetic energy)? Examples

Answer 16

energy associated with all electromagnetic waves, stored within the oscillating electric and magnetic field.
Examples: energy from the hot sun, energy from an LED

Question 17

What is meant by sound energy? Examples?

Answer 17

Energy of mechanical waves due to the movement of atoms. Examples: energy emitted when you clap, output of energy from your headphones

Question 18

What is meant by internal (heat or thermal) energy? Examples?

Answer 18

The sum of the random potential and kinetic energies of atoms in a system.
Examples: a hot cup of tea has more thermal energy than a cold one

Question 19

What does the principle of conservation of energy state?

Answer 19

The total energy in a closed system remains constant. Energy cannot be created or destroyed, it can only be transferred

Question 20

What is the formula of Kinetic Energy for an object in linear motion?

Answer 20

Ek = 1/2 m(v)2

Where m is mass and v is speed

Question 21

What is Ek directly proportional to?

Answer 21

Sq root of its speed

Question 22

How is Ek for objects travelling at same speed?

Answer 22

Directly proportional to their mass

Question 23

What is the formula of Gravitational Potential Energy?

Answer 23

Ep = mgh
where ms is mass, h is change in height, g is acceleration of free fall (9.81ms2 for objects close to earth)

Question 24

When is Ep lost?

Answer 24

When height decreases

Question 25

When is Ep gained?

Answer 25

When height increases

Question 26

What is the equation to calculated final speed form Ek and Ep? when is it valid?

Answer 26

v = square root of 2gh.
Only valid if there are no resistive forces
Derived from mgh = 1/2m(v)2

Question 27

What is power?

Answer 27

Power is the rate of work done

Question 28

Formula for power

Answer 28

P = W/t

Question 29

What is the unit pf measure of Power?

Answer 29

Js-1 or Watts (W). 1W=1Js-1

Question 30

How do you find speed when a constant force is needed to maintain a constant speed?

Answer 30

v = F/P

Question 31

What does the work-energy theorem state?

Answer 31

The work-energy theorem states that the work done on an object is equal to the change in its kinetic energy.

Question 31

Define efficiency

Answer 31

(Useful output energy/ Useful input energy) * 100%

Question 32

If you are given initial kinetic energy and work done how do you calculate Final Kinetic energy?

Answer 32

Initial kinetic energy - Work done = Final kinetic energy

Question 33

What is the definition of watt

Answer 33

Joule per second

Question 34

What is the relationship between P, the rate of work done against a frictional force, and the speed v of an object?

Answer 34

P directly proportional to (v)3

Question 35

What is the formula to calculate the work done by a couple?

Answer 35

work done = 2 × work done by each force

Question 36

Describe how the kinetic energy of the arrow changes during its journey from when it is fired until it reaches its
maximum height.

Answer 36

(Kinetic energy) reduces (with height)
At maximum height, KE is minimum

Question 37

What is the formula to calculated the total energy provided to do n activity when you are given the power output and the time the output is applied for (3.3. Q57)

Answer 37

E = P*t

Question 38

How do you calculate forward force if given power and velocity?

Answer 38

F = P/v