kinematics

Question 1

what is speed?

Answer 1

speed is the distance travelled per unit time

Question 2

what is the SI unit of speed?

Answer 2

m/s

Question 3

what is formula for speed?

Answer 3

average speed= total distance travelled per unit / total time taken

Question 4

what is the difference between uniform speed, average speed and instantaneous speed?

Answer 4

average speed = the speed that is assumed to be the same throughout the entire distance
uniform (or constant) speed = when the change in the distance travelled by an object for every unit of time is the same
instantaneous speed = the speed of an object at a particular instant

Question 5

what is the difference between distance and displacement?

Answer 5

distance =
1. the total length covered by a moving object regardless of the direction of motion
2. has magnitude only
displacement =
1. the distance measured in a straight line from a fixed reference point
2. has both magnitude and direction

Question 6

what is velocity?

Answer 6

velocity is the rate of change of displacement per unit time

Question 7

what is the SI unit of velocity?

Answer 7

m/s

Question 8

what is the formula for velocity?

Answer 8

average velocity = total displacement / total time taken

Question 9

what is acceleration?

Answer 9

acceleration is the rate of change of velocity (vector quantity)

Question 10

what is the SI unit of acceleration?

Answer 10

m/s2

Question 11

what are the causes of acceleration?

Answer 11

1. change in velocity
2. change in direction
3. both

Question 12

what is formula for acceleration?

Answer 12

acceleration = change of velocity (final - initial) / time taken
a = (v - u) / t

Question 13

what is the difference between uniform and non uniform acceleration?

Answer 13

uniform acceleration =
the constant rate of change of velocity
non uniform acceleration =
when the change in its velocity for every unit of time is not the same

Question 14

what is deceleration?

Answer 14

when an object is slowing down
final speed (v) is lower than its initial speed (u)

its acceleration will be a negative value (eg. acceleration = -0.60)
its deceleration is the positive value of its acceleration when it is slowing down (eg. deceleration = 0.60)

Question 15

what is acceleration of free fall?

Answer 15

• acceleration of free fall (for a body near to earth) is constant (regardless of mass/size)
  (ONLY IF THERE IS NO AIR RESISTANCE)
• approx. 10m/s2 (unless otherwise stated)
• due to gravity

Question 16

difference between free fall of objects with and without air resistance

Answer 16

free fall + absence of air resistance =
mass do not affect graph
v = d/t

free fall + presence of air resistance =
mass affects graph
w = air resistance (to reach terminal velocity)
increase with = 1. speed of objects 2. surface area of objects 3. density of air
^ mass = ^ W = ^ time for air resistance ro be equal to W = ^ terminal velocity

Question 17

what is terminal velocity?

Answer 17

terminal velocity is the maximum speed a falling object reaches when air resistance equals the weight, causing it to fall at a constant speed

Question 18

why do heavier objects fall faster in the presence of air resistance?

Answer 18

heavier objects fall faster because they need more air resistance to balance their greater weight, which only happens at higher speeds

Question 19

why do heavier objects have a higher terminal velocity than lighter ones?

Answer 19

their larger weight requires a greater air resistance to balance it, so they must fall faster to reach terminal velocity

Question 20

what is free fall?

Answer 20

free fall is the motion of an object under the force of gravity alone, with no air resistance
in free fall, all objects accelerate at 10 m/s² regardless of their mass/size