Physics Final STUDY-GUIDE PROBLEMS FOR THE FINAL I’ve tried to work these the best I can --- Animations and Spreadsheets Help Me a Lot. I’ll be incorporating these better in the future …

True / False Review

True False False False False 1. The rate at which velocity changes with time is called acceleration. 2. The SI unit of acceleration is meters per second. 3. When a car rounds a corner at a constant speed, its acceleration is zero. 4. A ball is thrown into the air. At the highest point of its path, the ball has zero velocity and zero acceleration. 5. As a ball falls freely, the distance it falls each second is the same. False False Anytime velocity or direction changes, acceleration must be changing. False For the same reason as #4: gravity is still acting on the ball. False The distance increases (remember the feather problem).

The amount of matter is the mass. WEIGHT is a force: False The amount of matter is the mass. WEIGHT is a force: 6. The amount of matter in an object is called the weight of the object. 7. The force due to gravity acting on an object is called the mass of the object. 8. The SI unit of force is called the kilogram. 9. If a hockey puck slides on a perfectly frictionless surface, it will eventually slow down because of its inertia. 10. Inertia is the resistance any material object has to a change in its state of motion. False See #6. False Force is in NEWTONS: False Newton’s Laws say an object keeps going unless something acts on the object. True

If Force goes up, Acceleration goes up. 11. The combination of all the forces that act on an object is called the net force. 12. The acceleration of an object is inversely proportional to the net force acting on the object. 13. Air resistance is caused by friction between the air and an object moving through the air. 14. The speed of an object dropped in air will continue to increase without limit until it strikes the ground. 15. When one object exerts a force on another object, the second object always exerts a force back on the first object. True False If Force goes up, Acceleration goes up. If Force goes down, Acceleration goes down. Therefore, F and a are DIRECTLY proportional. True False When the upward force of air friction equals weight, you stop accelerating. True

True Almost True But False False False False 16. A rocketship is pushed forward by gases that are forced out the back of the ship. 17. In order to make a cart move forward, a horse must pull harder on the cart than the cart pulls on the horse. 18. If a bicycle and a parked car have a head-on collision, the force of impact is greater on the bicycle. 19. A quantity that has both magnitude and direction is called a scalar. 20. A single vector can be replaced by two vectors in the X and Y directions. These X and Y vectors are called the resultant of the original vector. True Almost True But False If the horse was on ice, “pulling harder” couldn’t happen. It’s the ground (and friction) allowing pulling. The horse pushes on the ground, and the ground pushes back to move the horse and cart. False Newton’s 3rd Law – EQUAL BUT OPPOSITE FORCES. False A scalar is just a number: 6. A vector is magnitude AND direction. False Just the opposite – the two vectors can be replaced by the resultant vector.

Mass is just a number (no direction). 21. When a woman pushes a lawnmower along the handle, she pushes down as well as forward. 22. Mass is a vector quantity. 23. Wind velocity can be represented as a vector quantity. True False Mass is just a number (no direction). True Weathermen report “wind is 10 mph out of the north” --- both magnitude and direction.

INCLINED PLANE: A Quick Overview The incline doesn't allow the full affect of gravity. Gravity is trying to pull straight down, with a force: The part of gravity pulling down the incline is: 25.0 kg There's friction on the plane, opposing the slide with force: Net force on the plane is: FIRST THING TO DO … CALCULATE FORCE VECTORS Fg is calculated first

VECTOR ADDITION 20° East of North Vectors have both Magnitude and Direction (scalars are just magnitude). ORIGINAL VECTOR 20° East of North VECTOR COMPONENTS You must make a triangle by dropping the vector tail perpendicular to the x-axis. 20° E of N 70°

#1 What is the magnitude of the sum of the horizontal components of the following vectors? 12m @ 34˚E of N + 56m @ 78˚N of W + 91m @ 23˚ S of E

Make a Table (simplest way) avoid both of these mistakes VECTOR COMPONENTS You must make a triangle by dropping the vector tails perpendicular to the x-axis. VECTOR COMPONENTS Make a Table (simplest way) common mistake 1 using the wrong angle common mistake 2 using the right angle, but not including the proper sign with sin and cos. avoid both of these mistakes drawing the direction vectors - and then the angles.

ADDING VECTORS How Are Vectors Added, Geometrically? Everything is “Tip to Tail” Purple Vector (Tail) Added to Blue Vector (Tip)

ADDING VECTORS How Are Vectors Added, Geometrically? Everything is “Tip to Tail” Red Vector (Tail) Added to Purple Vector (Tip)

THE RESULTANT VECTOR

THE RESULTANT VECTOR ADDING VECTORS geometrically ADDING VECTORS With a Table

#2 FINDING MAGNITUDE FINDING DIRECTION (South of West) Add the following vectors: 12.3m North; 45.6m East; 78.9m West; 14.7m South. FINDING MAGNITUDE FINDING DIRECTION (South of West)

v #3 I need d. Find an equation with this, and see what I’m missing. A car travels 540km in 4.5hr. How far will it go in 8 hrs at the same average speed? I need d. Find an equation with this, and see what I’m missing. A Simpler Way? Using Proportions Use actual data from the trip. I need v

when there’s acceleration, the distance between points increases. #4 Bill’s motorcycle can accelerate at 7.05m/s2 at a certain RPM and gear. How far, starting from rest, will Bill travel in the first 2.50s? REMEMBER when there’s acceleration, the distance between points increases. I need d. Find an equation with this, and see what I’m missing. from rest After 2.5 seconds, he’s gone 22m.

#5 I need d. Find an equation with this, and see what I’m missing. Chuck’s car is traveling at 65.0m/s when he suddenly accelerates his car at 15.0m/s2 for 3.00s. How far did Chuck, and his car, travel while he was accelerating? I need d. Find an equation with this, and see what I’m missing. Each Represents 1 Second Accelerate for 3 seconds, at 15 m/s2.. The Distance Traveled during this time: d = 263 m Constant velocity of 65 m/s for 2 seconds

I need t Find an equation with this, and see what I’m missing. #6 An astronaut drops a feather from 1.2m above the surface of the moon. If the acceleration due to gravity is 1.62m/s2 on the moon; how long does it take the feather to reach the ground? I need t Find an equation with this, and see what I’m missing. Dropping an object from rest: vi = 0 Each dot = 1/5 of a second

Be careful not to just drop in the numbers! #7 Engineers are developing new types of guns that might someday be used to launch satellites as if they were bullets. One such gun can give a small object a velocity of 3.5km/s moving it through a distance of only 2.0cm. What is the acceleration of the object? PROPER UNITS! Be careful not to just drop in the numbers! I need a. Since there are a couple equations with a, which one includes vi and vf. Accelerating from rest, vi = 0

moving east with constant velocity #8 A box with a mass of 25.0kg is moving at a constant velocity across a horizontal surface because of a 75.0N force. Calculate the coefficient of friction acting on the box. moving east with constant velocity 25 kg I need force of friction. There’s only one equation, so let’s see what I need. REMEMBER The amount of matter in an object is the mass; WEIGHT is the gravity applied to mass (i.e., F = ma)

THINK ABOUT THE PROBLEM #9 A 438kg car is accelerating east at 2.55m/se. If the coefficient of friction felt by the car is 0.500; what is the total force acting east on the car? Accelerating east THINK ABOUT THE PROBLEM The car is accelerating east, but encountering huge friction forces trying to slow it down. The force exerted by the engine to overcome this must be huge!

#10 How much total force is needed to accelerate a 2.0kg block of wood at 4.0m/s2 along a rough table, against a force of friction of 10.N? 2 kg

I need d. Find an equation with this, and see what I’m missing. #11 A man with a mass of 1.0 x 102kg slides across a frozen lake with an initial speed of 5.5m/s. Friction slows him, and after 4.3s he comes to a stop. How far did he slide across the lake? What is acceleration? I need d. Find an equation with this, and see what I’m missing. I need a

#12 A 25.0kg box is on a 20.0m long incline that is at an angle of 37.0˚, with a coefficient of friction of .15. What is the boxes velocity at the bottom of the incline? What is the NET FORCE? The block is pulled down the plane with the part of gravity parallel to the plane: 147.4N The force of friction literally says, "Not so fast", slowing down the block with force 36.75N. 25.0 kg 37° 37° I need vf. Find an equation with this, and see what I’m missing. CALCULATE FORCE VECTORS Fg is calculated first I need a

Heading up the frictionless ramp #13 With what force does a 75.5kg person need to be pushed in order to go up a 22.8˚ frictionless incline at a constant velocity? 75.5 kg 22.8° Heading up the frictionless ramp 22.8°

I need vx. There’s only one equation with it: #14 Tom kicks a rock horizontally off of a 20.0m high cliff. How fast did he kick the rock if it hits the ground 45.0m from the base of the cliff? from rest I need vx. There’s only one equation with it: I need t Each dot = .25 seconds

I need dx. There’s only one equation with it: #15 Nicole throws a ball at 25m/s at an angle of 60˚ above the horizontal. What was the range of the ball? I need dx. There’s only one equation with it: I need t Each dot = .50 seconds

Be careful not to just drop in the numbers! #16 Calvin is walking down the street at 4.0km/hr. If he has a mass of 70.kg, what is his momentum? PROPER UNITS! Be careful not to just drop in the numbers!

#17 A 1.0x104kg freight car is rolling along a track at 3.0m/s. Calculate the time needed for a force of 1.0x102N to stop the car. I need a

Conservation of Momentum Be careful not to just drop in the numbers! #18 A 3.0g bullet moving at 2.0km/s strikes an 8.0kg wooden block that is at rest on a frictionless table. The bullet passes through and emerges on the other side with a speed of 5.0x102m/s. How fast is the block moving after the collision? 8 kg BEFORE COLLISION 8 kg AFTER COLLISION Law of Conservation of Momentum PROPER UNITS! Be careful not to just drop in the numbers!

After-Collision Momentum After-Collision Velocity #19 A 125kg cart with a momentum of 1250kgm/s east collides with a 225kg cart whose momentum is 2250kgm/s north. The two carts lock together. What is the velocity of the carts after the collision? After-Collision Momentum p2=2250 After-Collision Velocity if no collision: p2=2250 if no collision: p1=1250 Angle (North of East)

#20 . A 15kg ball is rolling across the floor at 2.0m/s. A force is applied for 2.0m which increases its velocity to 5.0m/s. Calculate the magnitude of the force. vi = 2 m/s vf = 5 m/s Additional Force: F = ? 15 kg 15 kg 15 kg 2 m I need a

#21 A 13.0kg box is lifted to a ledge that is 3.50m high in 8.00s. Calculate the power generated when moving the box.

a #22 I need vf. Find an equation with this, and see what I’m missing. A 24.5kg ball is rolling at 3.25m/s across a frictionless plane. If a 10.0N force is exerted for 2.00m on the ball, what will the new velocity of the ball be? vi = 3.25 m/s vf = ? 24.5 kg I push the ball with force 10N 24.5 kg 24.5 kg 2 m I need vf. Find an equation with this, and see what I’m missing. I need a