Mechanics

Question 1

Random errors

Answer 1

Random errors are errors in measurements that lead to measured values being scattered unpredictably about a mean.

Question 2

Systematic errors

Answer 2

Systematic errors are errors which lead to all measured values being either consistently greater or consistently lesser than the true value by a fixed value.

Question 3

accuracy

Answer 3

The accuracy of a set of experimental data is defined as a measure of how close the experimental values are to the true value of the physical quantity.

Question 4

precision

Answer 4

The precision of an experiment is defined as a measure of how close the experimental values are to each other.

Question 5

scalar

Answer 5

A scalar is a physical quantity that is completely specified by a value with an appropriate unit and has no direction.

Question 6

vector

Answer 6

A vector is a physical quantity that is completely specified by a value with an appropriate unit and that has direction.

Question 7

speed, velocity, acceleration

Answer 7

rate of change of distance travelled; rate of change of displacement; rate of change of velocity

Question 8

Hooke’s Law

Answer 8

Hooke’s law states that the extension x is directly proportional to the force F applied on the spring or wire (provided the limit of proportionality is not exceeded).

Question 9

Upthrust

Answer 9

Upthrust U is the resultant vertical upward force exerted by the surrounding fluid on a fully or partially submerged body as the pressure at the bottom surface is greater than that at the top.

Question 10

Archimedes’ Principle

Answer 10

Archimedes’ Principle states that when a body is wholly or partially immersed in a fluid, it is buoyed by an upthrust equal in magnitude and opposite in direction to the weight of fluid displaced by the body.

Question 11

Principle of Floatation

Answer 11

Principle of Floatation states that when a body is floating in equilibrium in a fluid, the upthrust on it is equal in magnitude to the weight of the body.

Question 12

CG (Centre of Gravity)

Answer 12

Centre of gravity of a body is the point where the weight of the body appears to act through.

Question 13

Moment of a force

Answer 13

Moment of a force about a point is defined as the product of the magnitude of force F and the perpendicular distance d of the point from the line of action of the force.

Question 14

Torque of a couple

Answer 14

Torque of a couple is defined as the product of one of the forces F and the perpendicular distance d between the lines of action of the forces, where the forces are equal in magnitude and opposite in direction and their lines of action do not coincide.

Question 15

(Static) equilibrium

Answer 15

Static equilibrium occurs when resultant force is zero in all directions and resultant torque is zero about any axis.

Question 16

Principle of Moments

Answer 16

Principle of moments states that if a body is in equilibrium, the sum of clockwise moments must be equal to the sum of anti-clockwise moments about any point.

Question 17

Linear momentum

Answer 17

The linear momentum p of a body is defined as the product of its mass m, and its velocity v and it is in the direction of the velocity.

Question 18

N1L

Answer 18

Newton’s First Law of Motion states that a body continues to be in a state of rest or uniform motion in a straight line (uniform velocity) unless acted on by a net external force.

Question 19

N2L

Answer 19

Newton’s Second Law of Motion states that the rate of change of momentum of a body is directly proportional to the net external force acting on it and it takes place in the direction of the net external force.

Question 20

N3L

Answer 20

Newton’s Third Law of Motion states that if a body A exerts a force on body B, then body B exerts a force of the same type (nature) of equal magnitude but opposite in direction on body A.

Question 21

weight

Answer 21

The weight of an object is defined as the resultant gravitational force acting on it due to gravitational field of (massive object). Given by mg.

Question 22

Conservation of Momentum (COM)

Answer 22

The principle of conservation of momentum states that the total momentum of a system remains constant before, during and after a collision provided that no net external force acts on the system.

Question 23

Work Done (WD)

Answer 23

The work done by the constant force is defined as the product of the force and displacement in the direction of the force.

Question 24

Power

Answer 24

Rate of work done

Question 25

Angular displacement

Answer 25

The angular displacement is the angle subtended at the centre of a circle in radians by arc length s in the anti-clockwise direction where it is equal to s/r with r being the radius of the circle.

Question 26

Angular velocity

Answer 26

rate of change of angular displacement

Question 27

Field (of force)

Answer 27

A field of force is a region of space where an object, with a property unique to that field, experiences a force.

Question 28

Newton’s Law of Gravitation

Answer 28

Newton’s law of gravitation states that **every point mass attracts every other point mass **with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Question 29

Graviational field strength

Answer 29

Gravitational field strength at a point is defined as the gravitational force exerted per unit mass on a small test mass placed at that point in the gravitational field.

Question 30

Gravitational Potential Energy (GPE)

Answer 30

Gravitational potential energy of a system of masses is defined as the work done by an external agent in bringing the masses from infinity to their positions in the system, without producing any acceleration.

Question 31

Gravitational Potential

Answer 31

Gravitational potential at a point in a gravitational field is defined as the work done per unit mass by an external agent in bringing a small test mass from infinity to that point, without producing any acceleration.

Question 32

escape velocity

Answer 32

The escape velocity is defined as the minimum initial velocity of any object that just allows the object to escape a planet’s (or any large celestial body’s) gravitational field and never return to the planet’s surface.

Question 33

Geostationary orbit

Answer 33

A geostationary orbit is one where the satellite will remain in the same position in the sky relative to the Earth’s surface.