Impuls and momentum

Impulse Momentum Cheat Sheet

Momentum

Momentum is a physical concept that is defined as “moving body”. In other words for talking about momentum we must have moving object, it must have both mass and velocity. Let me formulize what we said;

Momentum=Mass X Velocity=m.P

Where p is the momentum and m is the mass

Unit of the momentum is kg.m/s as you can guess from the equation.

Impulse

If you apply a force on an object 1 s then you see small change in the momentum. However, if you apply force on an object long period of time then you see the amount of change in momentum is bigger than the first situation. In summary, I try to say that impulse is the multiplication of applied force and time interval it applied. Impulse is also a vector quantity having both magnitude and direction. It has the same direction with applied net force.

Impulse=Force.Time Interval

Impulse and momentum are directly related to each other. Let’s find this relation now.

Impulse=Change in Momentum

Conservation of Momentum

If there is no force applied on the system then momentum of the system is conserved in magnitude and direction.

Pinitial=Pfinal

m1.V1=m2.V2

Collisions

Momentum is conserved in all collisions. If the objects collide and momentum and kinetic energy of the objects are conserved than we call this collision “elastic collision”. On the other hand if the momentum of the object is conserved but kinetic energy is not conserved than we call this type of collision “inelastic collision”.

To sum up, we can say that, momentum of the system is conserved in both elastic and inelastic collisions however; kinetic energy is conserved only in the elastic collisions.

Some problem of Work and Energy

Physics 1 - Work, Power, Energy Worksheet

1.  Calculate the work done by a 47 N force pushing a pencil 0.26 m.

2.  Calculate the work done by a 47 N force pushing a 0.025 kg pencil 0.25 m against a force   of  23 N.

3.  Calculate the work done by a 2.4 N force pushing a 400 g sandwich across a table 0.75 m wide.

4.  How far can a mother push a 20.0 kg baby carriage, using a force of 62 N, if she can only do 2920 J of work?

5.  How much work is it to lift a 20 kg sack of potatoes vertically 6.5 m?

6.  If a small motor does 520 J of work to move a toy car 260 m, what force does it exert?

7.  A girl pushes her little brother on his sled with a force of 300 N for 750 m.  How much work is this if the force of friction acting on the sled is (a) 200 N,             (b) 300 N?

8.  A 75.0 kg man pushes on a 500,000 t wall for 250 s but it does not move.  How much work does he do on the wall?

9.  A boy on a bicycle drags a wagon full of newspapers at 0.80 m/s for 30 min using a force of 40 N.  How much work has the boy done?

10.  What is the gravitational potential energy of a 61.2 kg person standing on the roof of a 10-storey building relative to (a) the tenth floor, (b) the sixth floor, (c) the first floor. (Each storey is 2.50 m high.)