Kinetic Energy Basic Questions and Answers

Kinetic energy is the energy of motion. If any object is moving, rotating that object contains kinetic energy. This tutorial we will briefly go through the kinetic energy basic questions. Importantly kinetic energy is scalar quantity, which means it does not have direction.

Equation:    Kinetic Energy = ½ * Mass of the Object * (Velocity) ²

 E = ½ MV²

 The unit of Kinetic Energy = J (Joule) = kg * (m/s) ²

Questions

1. Object “P” has Mass of 60 kg and velocity (speed) 120 ms^-1 at point A. what is the kinetic energy at point A?

2. When object “P” moves to it has a Kinetic energy of 6000J, what is the velocity of the object “p” at point B?

3. Then in point C Object “P” moves in vertical direction with 20 ms-¹ speed. What is the kinetic energy of object “p”?  In which direction?

4. Object P has a kinetic energy of 200J and object Q has a kinetic energy of 100J. Object Q has a velocity of 5 ms^-1.  Object P’s mass is twice of the Object Q’s mass. What is the velocity of object P?

Answers

Graph for Ques 1,2,3

1. Applying, E = ½ MV² at point A

E = ½ * 60 * (120) ²

E = 432000 J = 432 kJ

2. Applying, E = ½ MV² at point B

6000 = ½ * 60 * V²

V = 14.14 ms^-1

3. Applying, E = ½ MV² at point C

E = ½ * 60 * (20) ²

E = 12000 J = 12 kJ

As kinetic energy is a scalar quantity, which don’t have direction.

4.  

Applying, E = ½ MV² for Object P

200 = ½ * m_p * V_p^{2 ------------------------} A

Applying, E = ½ MV² for Object Q

100 = ½ * m_q * 5^{2 ------------------------} B

Given that,

2 m_{q =}  m_p ^{------------------------} C

From above 3, A/B

2 = (m_p / m_{q) *} (V_p² /  5² ) ^{------------------------} D

Applying (C) in above equation (D),

2 = (2 m_q / m_{q) *} (V_p² /  5² )

V_p = 5 ms^-1

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