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5.5 Questions

1.What does law of impulse(linear momentum) conservation state?

2 What's сenter of mass ?
3.What's mechanical work and what's the unit of work?
4.What's power and what's the unit of power ?

5.What's physical sense of energy?
5.Give the definition of kinetic energy.
6.Give the definition of potential energy.
7.What force is conservative one?

8. What does the law of energy conservation state ?
9 What are distinctions between perfectly inelastic and perfectly elastic
collisions ?

10.What are primary sources of alternative energy?
5.6 Problems
Ballistic Pendulum

The ballistic pendulum is a classic method of determining the
velocity of a projectile. It is also a good demonstration of some of the

basic principles of physics. The ball of mass m is fired with speed v m

into the pendulum of mass M.. From the height h reached by the
pendulum, we can calculate its potential energy E . This potential
P
energy is equal to the kinetic energy of the pendulum at the bottom of
the swing, just after the collision with the ball.
We cannot equate the kinetic energy of the pendulum after the

collision with the kinetic energy of the ball before the swing, since the
collision between ball and pendulum is inelastic and kinetic energy is
not conserved in inelastic collisions. Momentum is conserved in all

forms of collision, though; so we know that the momentum of the ball
before the collision is equal
to the momentum of the

pendulum after the
collision. Once we know
the momentum of the ball

and its mass, we can
determine the initial
velocity.
Begin with the

Figure 5.15 65