Mechanics

Question 1

Distance

Answer 1

Distance is the total length travelled by a moving object irrespective of direction of motion.

Question 2

Displacement

Answer 2

The displacement of an object from a reference point O is the linear distance and direction of the object from O

Question 3

Speed / velocity

Answer 3

Speed/velocity is the rate of change of distance/displacement travelled wrt time.

Question 4

Acceleration

Answer 4

Acceleration of an object is its rate of change of velocity wrt time.

Question 5

N1L

Answer 5

N1L states that every body continues to be In a state of rest of to move with constant velocity unless a net force acts on it

Question 6

N2L

Answer 6

N2L states that the rate of change of momentum of a body is proportional to the net force acting on it and occurs in the direction of the force

Question 7

N3L

Answer 7

N3L states that that if body A exerts a force on body B, body B will exert of force of the same type that is equal in magnitude and opposite in direction on body A

*cannot say the forces cancel out

Question 8

Inertia

Answer 8

Inertia of a body refers to its reluctance to start moving, and it’s reluctance to stop once it has begun moving m.

Question 9

Mass

Answer 9

Mass of body is a measure of its inertia, specifying how much resistance and object exhibits to changes in velocity.

Question 10

Weight

Answer 10

Weight of the body is the gravitational force acting on it towards the centre of the earth.

Question 11

Weightlessness

Answer 11

No contact force acting on object (free fall)

Question 12

Impulse (of a force)

Answer 12

Impulse (of a force) is the product of the average force acting on the object and the time interval over which it was applied.

Question 13

Momentum - impulse theorem

Answer 13

The change in momentum of a particle during a time interval equals the impulse of the net force that acts on the particle during that interval.

(integrate F-t)

Question 14

Linear momentum

Answer 14

Linear momentum of a body of constant mass moving with velocity is defined to be the product of mass and linear velocity.

Question 15

Principle of linear momentum

Answer 15

PCLOM states that when bodies in a system interact, the total momentum remains constant provided no external force acts on the system.

Question 16

Perfectly elastic collision

Answer 16

A ~ between 2 objects is one which the total KE is conserved; the relative speed of approach is equal to the relative speed of separation.

*use ke condition to solve verify if collision perfectly e

Question 17

Inelastic collision

Answer 17

An inelastic collision between two objects is one which the total KE of system of lower after collision than before. However momentum of an isolated system is always conserved.

Question 18

Head on collision

Answer 18

Lines of motion of both objects before and after collision are the same.

Question 19

Force

Answer 19

The resultant force acting on an object is given by the rate of change of momentum of an object.

Question 20

Field of force

Answer 20

Field of force is the region of space surrounding a body singing which it can exert a force on another similar body which may not be in contact with it.

• electric field is a region of space where a force acts on a stationary charge
• gravitational field is a region of space where a force acts on a mass
• magnetic field is a region of space where a force acts on a moving charge (current) or a North Pole.

Question 21

Contact force

Answer 21

A contact force is a force between two objects which has two components. The component perpendicular to the surface is the normal force, and the component parallel to the surface is the frictional force.

Question 22

Normal contact force

Answer 22

NCF is the net electrostatic repulsion between 2 surfaces in contact.

Question 23

Friction

Answer 23

Friction is the force that resists relative motion between two sliding surfaces (kinetic friction), or the tendency for relative motion between 2 stationary objects (static friction).

*f =kN; dependent on area in contact

Question 23

Viscous force (drag)

Answer 23

Viscous force is the resistive force that resists a body moving relative to a fluid.

Both viscous force and frictional force opposes relative motion but viscous force is dynamic while frictional force is static of kinetic

Question 24

Tension

Answer 24

Tension is the force which is transmitted through a string,rope cable or wire when pulled tight by opposite ends * medium must be taught if slack T=0 * usually medium and object inextensible

Question 25

Hooke's law

Answer 25

The magnitude of force F exerted by a spring on a body attached to the spring is directly proportional to the extension x of the spring from equilibrium, provided the proportional limit of the spring is not exceeded.

Question 26

Elastic potential energy

Answer 26

EPE in a deformed material is the area under a force extension graph

Question 27

Pressure

Answer 27

Pressure is defined as the normal force exerted per unit area.

Question 28

Upthrust

Answer 28

Upthrust is the net upward force exerted by a fluid on a body fully or partially submerged in a fluid.

Question 29

Derivation of pressure

Answer 29

* net horizontal force 0 * net vertical force = ro g a (height from water surface to bottom - height from water surface to top of object) aka difference between force acting on top surface and bottom surface

Question 30

Archimedes principle

Answer 30

Archimedes principle states that when an object is totally or partially immersed in a fluid in equilibrium, the Upthrust acting on the body is equal to the weight of fluid displaced.

Question 31

Principle of floatation

Answer 31

Principle of floatation states that a floating object in equilibrium displaced a weight of fluid (Upthrust) equal to its own weight.

Question 32

Principle of moments

Answer 32

Principle of moments states that for a system in (rotational) equilibrium, the sum of clockwise moments about any point is equal to the anticlockwise moments about that point.

Question 33

Centre of gravity

Answer 33

Centre of gravity of an object is the point at which the weight of the object appears to act

Question 34

Moment of a force

Answer 34

Moment of a force about a point is the product of the magnitude of the force and the perpendicular distance of the line of action of the force to the point.

Question 35

Couple

Answer 35

Couple is a system of forced which tends to produce a turning effect (rotation) only. A couple consists of two forces that are anti parallel, if equal magnitude and do not act along the same line of action.

Question 36

Torque of a couple

Answer 36

Torque of couple is the product of the perpendicular distance between the lines of action of the forces and the magnitude of one of the forces.

Question 37

Equilibrium

Answer 37

For a system in complete equilibrium, resultant force on the body must be 0 (translational equilibrium); resultant moment on the body about any axis must be 0 (rotational equilibrium)

Question 38

Principle of conservation of energy

Answer 38

Energy can be converged from one form to another but cannot be created or destroyed

Question 39

Work done by a force

Answer 39

The WD by a force on the body is the product of the magnitude of the force and the displacement in the direction of the force

Question 40

Power

Answer 40

Power is the rate at which work is done

Question 41

Instantaneous power

Answer 41

P = d WD / dt = Fv where is the instantaneous velocity

Question 42

1 rad

Answer 42

One rad is the angle subtended at the center of the circle by an arc equal in length to the radius of the circle

Question 43

Angular displacement

Answer 43

Angular displacement is the angle an object turns about a fixed point

Question 44

Angular velocity

Answer 44

Angular velocity is defined as the rate of change of angular displacement wrt time

Question 45

Period

Answer 45

Is the time taken for an object in circular motion to make one complete revolution

Question 46

Frequency

Answer 46

Is the the number of revolutions made per unit time