Physics By KruNit

The second note is built into this equation; momentum is a vector, and the momentum has the same direction as the velocity.

Impulse-Momentum Change Equation
In a collision, a force acts upon an object for a given amount of time to change the object's velocity. The product of force and time is known as impulse. The product of mass and velocity change is known as momentum change. In a collision the impulse encountered by an object is equal to the momentum change it experiences.

Impulse = Momentum Change

F • t = mass • Delta v

Again, this is a vector equation, so the change in momentum is in the same direction as the force.

CONSERVATION MOMENTUM

Types of collisions: (momentum is conserved in each case)

elastic - kinetic energy is conserved
inelastic - kinetic energy is not conserved
completely inelastic - kinetic energy is not conserved, and the colliding objects stick together after the collision.

The total energy is always conserved, but the kinetic energy does not have to be; kinetic energy is often transformed to heat or sound during a collision.

Impulse Momentum Exam and Problem Solutions

1. Objects shown in the figure collide and stick and move together. Find final velocity objects.

Using conservation of momentum law;

m₁.V₁+m₂.V₂=(m₁+m₂).V_final

3.8+4.10=7.V_final

64=7.V_final

V_final=9,14m/s

2. 2kg and 3kg objects slide together, and then they break apart. If the final velocity of m₂ is 10 m/s,

a) Find the velocity of object m₁.

b) Find the total change in the kinetic energies of the objects.

a) Using conservation of momentum law;
(m₁+m₂).V=m₁.V₁+m₂.V₂

5.4=30+2.V₁

V₁=-5m/s

b) E_Kinitial=1/2/m₁+m₂).V²

E_Kinitial=1/2.5.16=40joule

E_Kfinal=1/2.2.5²+1/2.3.10²

E_Kfinal=175 joule

Change in the kinetic energy is =175-40=135 joule

3. As shown in the figure below, object m₁ collides stationary object m₂. Find the magnitudes of velocities of the objects after collision. (elastic collision)

In elastic collisions we find velocities of objects after collision with following formulas;

V₁'=(m₁-m₂)/(m₁+m₂).V₁

V₂'=(2m₁/m₁+m₂).V₁

m₁=6kg, m₂=4kg, V₁=10m/s

V₁'=(6-4/6+4).10=2m/s

V₂'=(2.6/6+4).10=12m/s

4. Momentum vs. time graph of object is given below. Find forces applied on object for each interval.

F.Δt=ΔP

F=ΔP/Δt

Slope of the graph gives us applied force.

I. Interval:

F₁=P₂-P₁/10-0=-50/10=-5N

II. Interval:

F₂=50-50/10=0

III. Interval:

F₃=100-50/10=5N

5. A box having mass 0,5kg is placed in front of a 20 cm compressed spring. When the spring released, box having mass m₁, collide box having mass m₂ and they move together. Find the velocity of boxes.

Energy stored in the spring is transferred to the object m₁.

1/2.k.X²=1/2.mV²

50N/m.(0,2)²=0,5.V²

V=2m/s

Two object do inelastic collision.

m₁.V₁=(m₁+m₂).V_final

0,5.2=2.V_final

V_final=0,5m/s

Thank : http://www.physicstutorials.org/home/exams/impulse-momentum-exams-and-solutions/impulse-momentum-exam2-and-solutions

Simple machines

Simple machines make work easier for us by allowing us to push or pull over increased distances.

There are SIX simple machines:

Type	Example	Activity
1. Pulley - How Stuff Works A pulley is a simple machine that uses grooved wheels and a rope to raise, lower or move a load.		Pulleys
2. Lever - Enchanted Learning animations A lever is a stiff bar that rests on a support called a fulcrum which lifts or moves loads.		Levers
3. Wedge - pictures using LEGO bricks A wedge is an object with at least one slanting side ending in a sharp edge, which cuts material apart.		Wedges
4. Wheel & Axle - Activity using pencils and thread spools A wheel with a rod, called an axle, through its center lifts or moves loads.		Wheels
5. Inclined Plane - pictures using LEGO bricks An inclined plane is a slanting surface connecting a lower level to a higher level.		Inclined Planes
6. Screw - Activity using pencil and paper in a new way A screw is an inclined plane wrapped around a pole which holds things together or lifts materials.		Screws

Simple Machine Quiz

1. A fork is an example of a:

2. A bicycle is an example of a:

3. A bathtub is an example of a/an:
4. A swivel chair is an example of a:

5. A teeter totter on the playground is a:

6. You would use a pulley to:

Credit : http://www.mikids.com/SimpleMachines/smquiz.htm

Work energy and Power # 2

Power

The word “power” is most often associated with electricity in everyday use, but this is not the case in physics.

Power is the rate at which work is done.
This means that power measures how quickly energy is being used.
Since it is the rate at which something is happening, time must be involved somehow.
If you look at the basic formula for power, you’ll see that it is the same as many formulas that involve time.

P = power (Watts)
W = Δ E = work (Joules)
t = time (seconds)

Sometimes you will see Δ E instead of W in the above formula.

Δ E just means change in energy, which is what work is all about.

Power is really how fast you are using up energy, so it could be measured in Joules per second.

In honour of his search for a more efficient engine (which was better at converting energy!), the unit for power is called the Watt after James Watt.
Think of a light bulb… you always talk about how many Watts the bulb is, like a 60 W bulb.
That just means that the light bulb is using 60 Joules of energy every second.

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Energy Skate Park: Basics	Generator	Faraday's Electromagnetic Lab
Masses & Springs	My Solar System	Energy Skate Park
Gas Properties	Balloons & Buoyancy	States of Matter
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