3. Newton's third law
5. Conservation of momentum
<u>Explanation:</u>
Conservation of momentum is mostly used for describing collisions between objects. Here, the type of collision is inelastic collision in which the object when collides with the pendulum bob sticks to it and moves as a combined object. In this process the momentum is conserved.
Let the mass of the pendulum be m1 moving with a velocity v1.
Let the mass of the object be m2 moving with a velocity v2.
Since the momentum is conserved during collision, the equation will be
Where, v is the velocity of the combined system.
Conservation of momentum is actually a direct consequence of Newton's third law.
Consider a collision between two objects, object A and object B. When the two objects collide, there is a force on A due to B. However, because of Newton's third law, there is an equal force in the opposite direction, on B due to A
FAB = -FBA
The mechanical energy is not conserved due to the fact that the kinetic energy is not the same before and after the collision.
A motor turns electrical energy into mechanical energy.
A generator does exactly the opposite.
Answer:
d) The total mechanical energy is constant.
Explanation:
The total mechanical energy of a pendulum is given by:
where
KE is the kinetic energy (the energy of motion), given by
where
m is the mass of the pendulum
v is its speed
PE is the potential energy of the pendulum (the energy due to its position), given by
where
g is the acceleration due to gravity
h is the height of the pendulum relative to the ground
In absence of air resistance, the total mechanical energy of the pendulum is constant. This means that there is a continuous conversion of energy between kinetic and potential. In particular:
- When the pendulum is at its highest position (maximum displacement), the potential energy is maximum while the kinetic energy is minimum)
- When the pendulum crosses its equilibrium position, the kinetic energy is maximum (maximum speed) while the potential energy is minimum