1) Motion Forces and Energy

Question 1

scalar quantity

Answer 1

A scalar quantity is a quantity that has magnitude (size) only. Examples of scalars: distance, speed, time, mass, energy and temperature

Question 2

vector quantity

Answer 2

A vector quantity is a quantity has magnitude and direction. Examples of vectors: force, weight, velocity, acceleration, momentum, electric field strength and gravitational field strength

Question 3

speed

Answer 3

Speed is the distance travelled per unit time

Question 4

acceleration

Answer 4

Acceleration is the change in velocity per unit time

Question 5

velocity

Answer 5

Velocity is the speed in a given direction

Question 6

Average speed

Answer 6

Average speed is defined as total distance / Total time

Question 7

Free-fall

Answer 7

An object is in free-fall when it is moving only under the influence of the earth’s gravity.

Question 8

Acceleration of free fall

Answer 8

It is a value of the acceleration of free fall (g). On Earth, this value of g for any object that is near the surface is approximately constant at 9.8m/s2

Question 9

Mass

Answer 9

Mass is a measure of the quantity of matter in an object at rest relative to the observer

Question 10

Weight

Answer 10

Weight is defined as a gravitational force on an object that has mass

Question 11

gravitational field strength

Answer 11

ravitational field strength is the force per unit mass

Question 12

Spring constant

Answer 12

Spring constant is defined as the force per unit extension. Its formula is: k=F/x

Question 13

density:

Answer 13

Density is defined as the mass per unit volume

Question 14

Limit of proportionality:

Answer 14

It is a point beyond which the spring crosses its elastic limit and becomes permanently deformed.

Question 15

Newtons second law:

Answer 15

It states that, for a body of constant mass “m” and net force “F”, we can state that F = ma, where F ( net force) and a (acceleration)/ Both are vector quantities.

Question 16

Circular motion

Answer 16

Circular motion is defined as the movement of an object along the circumference of a circle or the rotation of an object along a circular path.

Question 17

Solid friction

Answer 17

Solid friction as the force between two surfaces that may impede motion and produce heating.

Question 18

Drag force

Answer 18

It is a force acting in a direction that is opposite to the relative motion of the object moving with respect to the surrounding fluid. Fluid refers to liquids and gases

Question 19

Moment of a force

Answer 19

It is a measure of the turning effect of a force. Formula is moment = force × perpendicular distance from the pivot. The SI unit of moment of a force is Nm

Question 20

Principle of moments

Answer 20

For an object in equilibrium, the sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments about the same point and the net force acting on it is zero

Question 21

Centre of gravity

Answer 21

It is a point at which the weight of a body or system is supposed to be concentrated. In uniform gravity it is the same as the centre of mass.

Question 22

Momentum

Answer 22

Momentum=mass × velocity; recall and use the equation p = mv. The SI unit of momentum is kgm/s

Question 23

Impulse

Answer 23

orce × change in time. [ it is the time for which force acts]. The Si unit of impulse is Newton-second (Ns)

Question 24

State the Principle of conservation of momentum

Answer 24

When 2 or more bodies interact (collide) in an isolated system, the total momentum stays the same.

Question 25

Define Resultant force

Answer 25

A resultant force is the change in momentum per unit time. The unit is Newtons (N)

Question 26

Define Kinetic energy

Answer 26

The energy possessed by an object, by virtue of its motion is called as kinetic energy.

Question 27

Define Gravitational potential energy

Answer 27

When objects are placed in a gravitational field, they possess certain energy relative to their position in this gravitational field. This energy is called as the gravitational potential energy. Formula for the gravitational potential energy= mgh; here m=mass of the object, g=gravitational field strength and h is the height to which the object is raised.

Question 28

Define Chemical energy

Answer 28

The energy stored in the bonds of chemical compounds is called as the chemical energy.

Question 29

Define Elastic (Strain energy):

Answer 29

Strain energy is the energy stored in an object due to its deformation.

Question 30

Define Electrostatic energy

Answer 30

It refers to the potential energy of a system of separated electric charges

Question 31

Define Internal (Thermal) energy

Answer 31

The energy of a thermodynamic system is its internal energy. It is the energy associated with the random, disordered motion of molecules

Question 32

State the Principle of conservation of energy

Answer 32

Principle of conservation of energy states that “ Energy can never be created nor destroyed. It can only be converted from one form to another. The total amount of energy in a system stays the same.

Question 33

Define Work

Answer 33

Work is= Force x displacement. Here the displacement is in the direction of the force. Unit of work is Joule.

Question 34

Define One Joule

Answer 34

One Joule refers to the work done by a force of 1 Newton, when it displaces a body through 1m in the direction of the force applied.

Question 35

Define Solar cells [ Photovoltaic cells]:

Answer 35

This refers to cells that are capable of converting light energy to electrical energy through photovoltaic effect

Question 36

Define Solar panels

Question 37

Define Wind energy:

Answer 37

The energy of the naturally flowing air that is used to generate electricity is called as wind energy.

Question 38

Define Renewable energy resources:

Answer 38

This is the type of energy that comes from resources that are easily replenished. Example: Energy from the sun, wind, etc.

Question 39

Define Non-renewable energy:

Answer 39

This is the type of energy that comes from resources that are easily not easily replenished. Example: Energy from fossil fuels

Question 40

Define Percentage Efficiency:

Answer 40

Percentage efficiency= {[ Useful energy output] /Total energy input]} x 100 or { [ Useful power output] /Total power input]} x 100

Question 41

Define Power

Answer 41

Power is defined as the work done per unit time of power is defined as the energy transferred per unit time.SI unit power is Watts (W)

Question 42

Define Pressure:

Answer 42

Pressure is defined as the force per unit area.SI unit of pressure if Pascals (Pa). Formula for calculating pressure due to solids=Force/Area; While the formula to calculate the pressure exerted due to liquids is=hpg. Where h is the height of the liquid column, p is the density of the liquid and g is the gravitational field strength.