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# Physics THS

### Physics Mid-term THS

Question | Answer |
---|---|

Projectile p147 | object shot through the air or is an object that moves through the air by virtue of its own inertia |

trajectory p153 | the object's (that was shot through the air) path through space |

Uniform circular motion | is the movement of an object at a constant speed around a circle |

Uniform circular motion requires that the object MUST move at a constant speed | therefore it can only move in a horizontal circle - one in which gravity is always perpendicular to the object's tangential velocity. |

An object is said to be moving in uniform circular motion | when it maintains a constant speed while traveling in a circle |

acceleration is a vector quantity comprised of both magnitude and direction, objects can accelerate in any of these three ways | 1. constant direction, changing speed (linear acceleration); 2. constant speed, changing direction (centripetal acceleration); 3. change in both speed and direction (angular acceleration). |

When moving in vertical circles, | the object’s speed is always changing and the object is NOT considered to be moving in uniform circular motion. |

What is Linear acceleration | when an object accelerates Constant direction AND Changing SPEED |

What is centripetal acceleration | when an object accelerates Constant speed AND Changing directions |

What is angular acceleration | when an object accelerates BOTH speed AND Direction CHANGE |

define: Centripetal Force | Is the Net force toward the center of the circle |

define: Physics | is a branch of science that involves the study of the physical world. |

define: dimension analysis | the method of treating the units as algebraic quantities |

define: significant digits | he valid digits in a measurements |

define: scientific method | a method of observing , experimenting , and analyzing answers to questions about the natural world. |

define: hypothesis | an educated guess about how variables relate |

define: hypothesis | is a RULE of nature that SUMS UP related OBSERVATIONS to DESRCIBE a PATTERN in NATURE |

define: scientific Theory | is an EXPLANATION based on many observations SUPPORTED by EXPERIMENTAL results |

what is force? | _____is the Push or Pull on an object |

What is a Free Body Diagram? | _____is a physical model. Its when all the FORCEs are summarized in a physical model. |

What is Net force? | _____vector sum on all forces on an object (whats vector sum Camille?) You are speaking about ALL of the forces acting on one, unique object |

inertia | The tendency of objects to resist change in their state of motion is called _____. |

How is Inertail measured? | Inertia is measured quantitatively by the object's mass |

Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. This is because a _________is defined as the interaction between two objects. The push and pull on an object. | Force |

How is Force measured? | They are measured in a unit called a newton |

Things to know about force as well | reaction, both of which constitute the interaction between one thing and the other. Neither force exists without the other. Since action and reaction forces act on different objects, action and reaction forces can never cancel each other. |

the object is said to be in a state of equilibrium: | If the forces cancel each other, then the net force acting on the body is equal to zero. When this happens, the object is said to be in |

static equilibrium | __________occurs when the object is at rest. |

dynamic equilibrium | _________occurs when the object is moving at a constant velocity. |

object will accelerates when ___________ | object will accelerate. The acceleration is directly proportional to the unbalanced force and is inversely proportional to the object's mass. Symbolically this is written as a ~ F/m |

Isaac Newtons 3 laws of Motion: | Law of Inertia / Law of Acceleration / Law of Action-Reaction |

Law of Inertia | An object maintains a constant velocity until an unbalanced, outside force acts upon it. OR , An object at rest will remain at rest, while an object moving at a constant velocity will continue to be in motion until it is acted upon by an outside force. |

Law of Acceleration | The acceleration an object experiences is directly proportional to, and in the same direction as, the net force acting upon it and is inversely proportional to the object's mass ( net F = ma ) |

Law of Action-Reaction | object A exerts a force on object B then object B exerts an equal but opposite force on object A ( FAB = - FBA ) |

freefall | means that the only force acting on the projectile is gravity; that is, there is no air resistance present. While in freefall, all projectiles experiences a unique value for their vertical acceleration: a = -g = -9.81 m/sec2. |

trajectory is also | projectile’s path through the air. If the projectile has vertical velocity, its trajectory traces a vertical line. When it has a horizontal velocity combined with a vertical velocity which is uniformly accelerated, the trajectory will be parabolic. |

The term apex | means highest point in the projectile’s trajectory where its instantaneous vertical velocity equals 0. |

A projectile is shot with an initial velocity of 400m/sec at an angle of 60 degrees to the horizontal. Vi = 400m/sec | cos (60 deg) = vx / (400 m/s)vx = 400 m/s • cos (60 deg) = ? m/ssin (60 deg) = vy / (400 m/s)vy = 400 m/s • sin (60 deg) = ? m/s |

Practice A: A water balloon is launched with a speed of 40 m/s at an angle of 60 degrees to the horizontal. Calculate Vix/Viy /time to reach Ymax(Tup) / Tot time of flight /Max Height ,range of projectileand final velociy before hitting the ground | cos (60 deg) = vx / (40 m/s)vx = 40 m/s • cos (60 deg) = 20.0 m/ssin (60 deg) = vy / (40 m/s)vy = 40 m/s • sin (60 deg) = 34.6 m/s |

Practice B: A motorcycle stunt person traveling 70 mi/hr jumps off a ramp at an angle of 35 degrees to the horizontal. Calculate Vix/Viy time | cos (35 deg) = vx / (70 mi/hr)vx = 70 mi/hr • cos (35 deg) = 57.3 mi/hrsin (35 deg) = vy / (70 mi/hr)vy = 70 mi/hr • sin (35 deg) = 40.1 mi/hr |

Practice C: A springboard diver jumps with a velocity of 10 m/s at an angle of 80 degrees to the horizontal. Calculate Vix/Viy time | cos (80 deg) = vx / (10 m/s)vx = 10 m/s • cos (80 deg) = 1.7 m/ssin (80 deg) = vy / (10 m/s)vy = 10 m/s • sin (80 deg) = 9.8 m/s |

the point of resolving an initial velocity vector into its two components is | to use the values of these 2 components to analyze a projectile's motion and determine such parameters as the horizontal displacement, the vertical displacement, the final vertical velocity, the time to reach the peak of the trajectory, the time to fall |

Determination of the Time of Flight | See NOTES tup = Viy/g |

The time for a projectile to rise vertically to its peak (as well as the time to fall from the peak) is dependent upon | vertical motion parameters. |

The process of rising vertically to the peak of a trajectory is a vertical motion and is thus dependent upon the ________________ | initial vertical velocity and the vertical acceleration (g = 9.8 m/s/s, down). |

acceleration is the rate at which the velocity of an object changes. T/F? | True |

To say that a projectile has a vertical acceleration of -9.8 m/s/s is to say that | the vertical velocity changes by 9.8 m/s (in the - or downward direction) each second |

FORMULA: time for a projectile to rise to its peak | is a matter of dividing the vertical component of the initial velocity (viy) by the acceleration of gravity. tup = Viy/g |

Determination of Horizontal Displacement | The horizontal displacement of a projectile is dependent upon the horizontal component of the initial velocity. The horizontal displacement of a projectile can be determined using the equation x = Vix * T |

If a projectile has a time of flight of 8 seconds and a horizontal velocity of 20 m/s, Calculate Horizontal Displacement | then the horizontal displacement is 160 meters (20 m/s • 8 s). |

If a projectile has a time of flight of 8 seconds and a horizontal velocity of 34 m/s, Calculate Horizontal Displacement | then the projectile has a horizontal displacement of 272 meters (34 m/s • 8 s) |

the horizontal velocity (symbols) | (vix). |

Determination of the Peak Height | y = viy • t + 0.5 • g • t2 Where viy is the initial vertical velocity in m/s, g is the acceleration of gravity ( -9.8 m/s/s) and t is the time in seconds it takes to reach the peak |

A projectile | is an object upon which the only force acting is gravity |

examples of projectiles. | An object dropped from rest / An object which is thrown vertically upward / And an object is which thrown upward at an angle to the horizontal (provided that the influence of air resistance is negligible to all). |

By definition, a projectile has only one force acting upon it - the force of gravity. If there was any other force acting upon an object, then that object would not be a projectile. True / False | True |

free-body diagram of a projectile | would show a single force acting downwards and labeled force of gravity (or simply Fgrav). Regardless of whether a projectile is moving downwards, upwards, upwards and rightwards, or downwards and leftwards |

A force is not required to keep an object in motion True or False? | True |

A force is only required to maintain an acceleration. True/False | True |

According to Newton's first law of motion, such a cannonball would continue in motion in a straight line at constant speed. If not acted upon by an unbalanced force, " | Example to Newton's 1st law in GRAVITY FREE ATMOSPHERE. |

Give example for each opf Newton's laws | ??? |

The speed of a satellite in circular orbit is constant. Tue / False? | True |

Johannes Kepler (1571-1630). | three empirical laws were published about the properties of satellites in elliptical orbits satellites which have variable speeds since their distance from the earth is constantly changing. |

Kepler's 1st Law: The Law of Elliptical Orbits | Each planet travels in an elliptical orbit with the sun at one focus. |

P. Sun C A | When the planet is located at pt P it is at the perihelion position.RP = distance from Sun to P and is called the perihelion radius. |

P. Sun C A | When the planet is located at point A it is at the aphelion position.RA = distance from Sun to A and is called the aphelion radius. |

P. Sun C A | The distance PA = RP + RA is called the major axis which is represented mathematically in formulas as 2a. |

Kepler’s 2nd Law: The Law of Equal Areas | A line frm dplanet to dsun sweeps out=areas of space in=intervals of tme. @dperihelion, the pt. closest 2 sn alng dplanet’s orbital path, dplanet’s speed is maximal. @aphelion,dpt farthest dsun along dplanet’s orbital path, dplanet’s speed is minimal. |

Kepler’s 3rd Law: The Law of Periods | The square of a planet’s orbital period is directly proportional to the cube if its average distance from the sun |

Work | Is a product of FORCE Work = Force * dwhere F is Force and d is displacement |

When a force acts upon an object to cause a displacement of the object | Work |

three key ingredients to work | 1) force, 2) displacement, 3) cause. In order for a force to qualify as having done work on an object, there must be a displacement and the force must cause the displacement |

Examples of Work | horse pulling a plow through the field, a father pushing a grocery cart down the aisle of a grocery store, a freshman lifting a backpack full of books upon her shoulder, a weightlifter lifting a barbell above his head, an Olympian launching the shot-put |

A teacher applies a force to a wall and becomes exhausted. Is this Work? Why/Why not? | This is not an example of work. The wall is not displaced. A force must cause a displacement in order for work to be done. |

A book falls off a table and free falls to the ground. Is this Work? Why/Why not? | This is an example of work. There is a force (gravity) which acts on the book which causes it to be displaced in a downward direction (i.e., "fall"). |

Mathematically, work can be expressed by the following equation. | W = F * d * cos Owhere F is the force, d is the displacement, and the angle (theta) is defined as the angle between the force and the displacement vector. |

A 10-N forces is applied to push a block across a friction free surface for a displacement of 5.0 m to the right. Solve Forces doing work on an object & Amt of work done by each force | Only Fapp does work. Fgrav and Fnorm do not do work since a vertical force cannot cause a horizontal displacement / Wapp= (10 N) * (5 m) *cos (0 degrees) = +50 Joules |

A force of 50 N acts on the block at the angle 30 degrees shown in the diagram. The block moves a horizontal distance of 3.0 m. How much work is done by the applied force? | W = F * d * cos(Theta) W = (50 N) * (3 m) * cos (30 degrees) = 129.9 Joules |

Newton | first thought of the concept of a “quantity of motion” made up of mass and velocity. We call it momentum |

Some typical interactions involving momentum | Collisions Explosions Recoil |

define: Momentum | The product of an object’s mass and its velocity. The direction of the momentum of an object is the same as the direction of its velocity |

Momentum is the product of an object’s ______ and its velocity | mass |

The direction of the momentum of an object is the _____as the direction of its _____ | same / velocity. |

Since p = mv, the units for momentum | are kg·m/s |

a 10.0 kg mass travelling [E] at 20.0 m/s has a momentum of | (10kg*20m )s = 200. kgm/s |

Momentum is really a measure of the difficulty encountered in bringing an object to rest. The greater the mass or velocity of an object, | the bigger its momentum |

Law of Conservation of Momentum | Momentum is a “conserved” quantity. In a closed system, the total momentum before the interaction takes place equals the total momentum after the interaction |

A fully loaded Redi-Mix cement truck has mass 42 000 kg travels north at 70. km/h. a) Calculate its momentum. b) How fast must a Toyota Matrix of mass 1270 kg travel in order to have the same momentum as the truck? | A) p = mv 70. km/h 19.4 m/s p = 42 000 kg * 19.4 m/s p = 814 800 kgm/s [N] p = 8.1 x 105 kgm/s B) p = mv so v = p/m = 814 800 kgm/s /1270 kg v = 642 m/s |

Saku Koivu has mass 90. kg skates towards Biron who has mass 100. kg. If Koivu is skating at 40. km/h, how much momentum does he have when he crashes into Biron? If they become entangled i.e. stick together, how fast do they travel? | p= mv (90. kg)(11.111 m/s) = 1.0 x 103 kgm/s (toward Biron)v = p/(m1 + m2) = (999.999 kgm/s)/(190 kg) = 5.26 m/s |

Originally, Newton thought that a force was needed to bring about a change in an object’ s motion i.e a force is required to produce a change in an object’s momentum. | Symbolically, this can be represented as F= ∆p/ ∆t F = m∆v/ ∆t F = ma |

Impulse | impulse is directly proportional to the applied force. Double the force, double the impulse. Impulse is also directly proportional to the time for which the force is applied - twice as long means twice the impulse, |

Impulse | Impulse is the product of the force and the time.Impulse = (force)(time) = FtImpulse is a vector quantity. It has the same direction as the applied force. |

So, the impulse exerted on an object depends directly on both how much force is applied and for how long the force is applied. T/F? | True |

Impulse Formula | Impulse = (force)(time) = FtImpulse is a vector quantity. It has the same direction as the applied force. Impulse = F t where F =force t=time |

You can get the same impulse by applying a large force for a short time, or applying a small force for a long time. T/False? | True |

Calculating Impulse: | Calculating the impulse exerted on an object by some force - impulse is always the product of the force and the time the force is applied. Since it is always the product of a force and a time, impulse has units like "Newton seconds". |

A force of 5 Newtons acts on a ball for 4 seconds. How much impulse was exerted on the ball? | Impulse = (force)(time) = (5 Newtons)(4 seconds) = 20 Ns |

The quantity Ft is called __________ | Vector quantity called Impulse |

The unit of momentum in SI is ______ | |

Calculating Momentum | multiply the object's mass times its velocity.A ball of mass 2 kg. is moving with a speed of 4 m/s. What is its momentum?Momentum = (mass)(velocity) = (2 kg)(4 m/s) = 8 kg m/s |

Momentum is NOT Inertia True/False | True |

An object has rest has NO Momentum. T/False | True |

What is the relationship between impulse and momentum? It is simple - and extremely powerful. The impulse-momentum equation says: | The Impulse applied by Net Force on a system = CHANGE of Momentum of the system |

"Impulse = Change in Momentum" | The impulse-momentum equation can be easily derived from kinematics and Newton's Second Law. This equation is very closely related to Newton's Second Law - in fact, it is often called the "Impulse-Momentum form of Newton's Second Law". |

Formula for Impulse Momentum | ? |

The unit of momentum in SI is_____ or,What is the SI unit for measuring momentum? | The SI unit of Momentum is the kilogram metre per second, or Newton seconds. (kg*m)/s or N*s, respectively. |

The most common symbol for momentum is p. The SI unit for momentum is kg m/s. | p=mv ( p momentum m mass v velocity ) |

The change of momentum for an object is equal to and caused by the _________ given to the object | Impulse (pls check) |

Any gain of momentum for an object occurs only by the _____ of a corresponding amount of momentum of another object | equal and opposite (pls check) |

Complete the equation FT = | ? |

In a system consisting of objects upon which, no external force is acting, the momentum of the system is ____ | Conserved (kindly check) |

2 objects of equal mass approach each other head-on with the same speed. The total momentum of the system before the collision takes place = | ? |

Momentum is a vector quantity. True/False | True |

Two train cars of equal mass collide inelastically. One car is at rest. The new velocity of the two cars together will be twice as great as the velocity of the first car True/False? | ? |

Which has more momentum, a large truck at rest on the freeway or a small car moving at 10 miles per hour on a street? | a) large truck b) small car c) both have the same momentum |

If the momentum of an object changes and its mass remains constant, then . . | a) its velocity is changing c) there is a force acting on it b) it is accelerating (or decelerating) d) All of the above |

Johnny hits a 0.050 kg golf ball, giving it a speed of 75 m/s. What impulse does he impart? | |

Any gain of momentum by an object occurs only by the _______ of a corresponding amount of momentum by another object. | |

In a system consisting of objects upon which no external force is acting, the momentum of the system is _____________. | |

Two objects of equal mass approach each other head-on with the same speed. The total momentum of the system before the collision takes place equals ___________. | |

If the momentum of a cannon is considered positive after it fires a shell, the momentum of the shell is considered ____________. | |

A moving object containing a bomb explodes. If the object had a total of 20 units of momentum just before the explosion, its pieces would have a total of _____ units of momentum just after the explosion. | |

Billiard ball A collides with billiard ball B, which is motionless on a table. During the collision, ball A loses 10 N-s of momentum. Which of the following is a possible condition for ball B after the collision? | a) m = 5 kg, v = 5 m/s c) m = 10 kg, v = 1 m/s b) m = 10 kg, v = 5 m/s d) m = 1 kg, v = 20 m/s |