dynamics

Question 1

Newton’s 1st Law of Motion

Answer 1

body stays at rest or continue to move at constant velocity unless a resultant force acts on it.

Question 2

Newton’s 2nd Law of Motion

Answer 2

the rate of change of momentum of a body is directly proportional to the net force acting on it, and, the direction of momentum change is in the direction of the net force.

Question 3

Newton’s 3rd Law of Motion

Answer 3

whenever a force acts on a body, an equal but oppositely directed force of the same kind acts on another body

Question 4

characteristic of action-reaction pair

Answer 4

-same nature
-equal magnitude
-act along same line but opposite directions
-act on different bodies

Question 5

linear momentum

Answer 5

product of the mass of an object and its velocity (p=mv)

Question 6

force

Answer 6

is the rate of change of momentum of an object which is free to move, and acts in the direction of the change in momentum.

Question 7

the Newton

Answer 7

is the SI unit of force. 1N is that force required to give a mass of 1kg an acceleration of 1m/s² in the direction of the force.

Question 8

moment of a force

Answer 8

moment of a force about any point is the turning effect of a force which is equal to the product of the force and the perpendicular distance from that point to the line of action of the force. (moments = fd)

Question 9

couple

Answer 9

consists of 2 forces of equal magnitude but acting in opposite directions whose lines of action are parallel but separate.

Question 10

torque of a couple

Answer 10

is the turning effect of the couple. for 2 equal but opposite parallel forces, each of magnitude F, with their lines of action separated by a perpendicular distance, d, the magnitude of the turning effect of the couple is the product of F and d.

Question 11

principle of moments

Answer 11

for a body to be in equilibrium, the sum of clockwise moments about any pivot must be equal to the sum of anti-clockwise moments about that same pivot.

Question 12

equilibrium

Answer 12

an object which, under the action of a number of forces, remains at rest or moving with a constant velocity and if in rotation is rotating at constant angular velocity is said to be in equilibrium.

Question 13

2 conditions for equilibrium

Answer 13

1. algebraic vector sum of the forces acting on the object in any direction must be 0.
2. algebraic vector sum of the moments of the forces in the object about any point must be 0.

Question 14

mass

Answer 14

measure of a body’s resistance to change in velocity.

Question 15

density

Answer 15

the mass per unit volume of a substance.

Question 16

weight

Answer 16

force acting on a mass due to a gravitational field.

Question 17

apparent weight

Answer 17

the normal contact force experienced by an object in contact with a surface.

Question 18

impulse

Answer 18

the product of the average force acting on an object and the duration of time for which the force acts.

Question 19

principle of conservation of linear momentum

Answer 19

the total linear momentum of a system will remain constant if no net external force acts on it.

Question 20

isolated system

Answer 20

a system which has no external force and no external torque acting on it, and, has no transfer of mass in and out of it.

Question 21

head-on collision

Answer 21

velocities of the colliding bodies are collinear both before and after impact

Question 22

elastic collision

Answer 22

a collision in which the total KE of the colliding bodies is conserved before and after the collision. relative velocity of separation is equal to the velocity of the approach.

Question 23

inelastic collision

Answer 23

total KE of the colliding bodies is NOT conserved before and after collision.

Question 24

perfectly inelastic collision

Answer 24

total KE of the colliding bodies is NOT conserved before and after collision, and the colliding bodies stick together after collision.