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Answers
Answer:
3). Speed = distance/time
Speed= 72/4
Speed = 18 Km/h
Explanation:
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Explanation:
2) Let OE = time, t
Now, from the graph,
BE = AB + AE
⇒ v = DC + OD (Since, AB = DC and AE = OD)
⇒ v = DC + u (Since, OD = u)
⇒ v = DC + u ------------------- (i)
Now, Acceleration (a) = Change in velocity / Time taken
⇒a = v−u / t
⇒a = OC − OD / t = DC / t
⇒at = DC -----(ii)
By substituting the value of DC from (ii) in (i) we get
v = at + u
⇒v = u + at
Above equation is the relation among initial vlocity (u), final velocity (v), acceleration (a) and time (t). It is called first equation of motion.
3) Distance, S=72 km
Time, t = 4 hr
Speed = 72 / 4 km/hr
= 72/4 × 5/18
=5 m/s
4) a) Kinetic Energy:
The energy possessed by an object due to its motion is called as kinetic energy.
Derivation:
Let us consider an object of mass "m" which is at rest on smooth horizontal plane.
Let a Force ,F acts on the object and let the object from rest moves from point A to point B and covers a displacement S.
The Work done by Force on the object is :
Work done = Force x displacement.
W=F×S ____(1).
From third equation of motion;
V² − U² = 2aS
S = V² − U² / 2a ______(2)
By Newtons second law of motion:
F = ma
From equation 1 and 2
W = m∗a∗(V² − U²) / 2a
As we have assumed object is at rest, U=0
W = mV² / 2
The Work Done appears as kinetic energy of the body.
Therefore,
K.E=( 1 / 2 )mV²
b) The law of momentum conservation can be stated as follows. For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision.
For example; when two balls in isolated system collide together, they will exert force on one another. The force applied on the balls will change the momentum of both the balls. The momentum of these both balls before and after collision would be the same. This is known as the law of conservation of momentum .
