PY131 Final Exam Review
Newtons
unit of force also Weight represents force required to accelerate a mass of 1kg by 1 m/s in 1 sec
A balloon is buoyed up with a force equal to the
weight of air it displaces
A skydiver's terminal velocity will be GREATEST if she falls
head first (smallest air resistance in this body position) parachute being open, or lying flat on back or stomach would cause more resistance
Specific heat deals with...
heat transfer
An educated scientific guess is a:
hypothesis
Roll a bowling ball off the edge of a table. As it falls, its horizontal component of velocity
remains constant
Bullet is dropped into a river from a very high bridge at the same time another bullet is fired straight downward from a rifle. Neglecting air resistance, the acceleration just before striking the water is
the SAME for each bullet b/c air resistance is neglected!!
Heat conductivity deals with...
touch
Padded dashboards in cars are safer in an accident than non-padded ones because passengers hitting the dashboard encounter:
- Lengthened (increased) time of contact - Increased impulse Decreased momentum= smaller force, longer time Impulse formula: Ft= change in (mass x velocity) Momentum= (mass x velocity)
5 kg shark swimming at a speed of 1 m/s swallows a 1kg fish swimming towards it at 5 m/s. The speed of the shark AFTER this meal is:
0 m/s Law of conservation of momentum Remember to make speed of fish negative because he was moving in OPP direction! Shark & fish stick together for one Vf so use m1v1 + m2v2= (m1+m2)Vf
You make one rotation around the 30 mile belt line in 30 mins. What is your avg velocity?
0 miles/hr Same start and end point. Avg velocity= displacement/ time Velocity is diff than speed!!
Two identical objects in outer space, on moving at 2 m/s, other at 1 m/s, have a head-on collision and stick together. Their combined speed after the collision is:
0.5 m/s formula for when two objects collide & stick together: m1v1 + m2v2= (m1+m2) Vf remember that momentum is conserved and momentum moving in opp directions in this example since its a head-on collision
The time it takes a projectile fired straight up at 10m/s to reach the top of its path is about
1 s since gravity working on it with a force of -10m/s^2
A block pulled to the left with 15 N and to the right with 5N at the same time experiences a NET force of:
10 N 15 N- 5N= 10N
A man leans over the edge of a cliff and throws a rock upward at 5 m/s. How far below the level from which it was thrown is the rock 2 secs later?
10 m Use displacement equation, solve for Xf: Xf= Xo+ Vot+ 1/2at^2
5 kg block, initially at rest, is allowed to slide down a frictionless incline from a height of 10m above the ground. How fast is the block moving on the ramp when it is only 5m above the ground?
10 m/s PE=mgh at top of ramp then halfway down at 5m mark it is 1/2 KE and 1/2 PE. Use KE= 1/2mv^2 to solve for velocity
A rock is thrown vertically into the air. At the top of its path, its acceleration is
10 m/s^2 Speed/ velocity would be 0 but acceleration remains constant or rock would freeze/ stop in path
To increase the temp of 50 g of water by 2 C degrees requires
100 calories 1 cal of E per 1g to increase by 1 degree C
A block held 1m under water experiences a buoyant force of 10N. If the block is pushed down to 2m under water the buoyant force will be:
10N Depth of object does NOT influence its Buoyant Force. Pressure on both bottom and top of object increase as it gets deeper but does NOT mean BF is greater.
A 2,000 kg car experiences a braking force of 10,000 N and skids to a stop in 3s. The speed of the car just before the brakes were applied was
15 m/s Uses acceleration & force equations
Car moving at 50 km/hr skids 20m with locked brakes. How far will the car skid with locked brakes if it were traveling at 150 km/hr?
180m Sliding friction example Use Law of Conservation of Energy Fd= Work= Change in E, so Fd= 1/2mv^2 and (d= 1/2 mv^2/F) Set two diff car situations equal to one another and solve for d2.
If a stone falls to the bottom of a mineshaft in 6s, the depth of the shaft is about:
180m x= 1/2gt^2 h and v originally are 0
If a projectile is fired straight up at speed of 10 m/s, the total time to return to its starting position is about
2 secs Travels distance of 20m in 2 s= 10m up then 10m back down to starting point
5000 N car, traveling at 20 m/s slides to a stop in 50m. How much force was applied to the car?
2,000N N means that 5,000 N required to move 1 kg of the car by 1m/s in 1 sec. It moved 50m therefore 50s. a= change in v/ t= .4 m/s^2. multiply this acceleration by original weight to find how much force must be applied to the car.
The avg breaking force of a 1000-kg car moving at 10 m/s braking to a stop in 5s is:
2000 N Uses F=ma and acceleration formula
A pulley system supports a 15N weight. System has 5 ropes supporting the weight and the worker pulls with 1, the system has a 1:5 ratio. How far must the worker pull their rope in order to raise the weight by 5m?
25m? 1/5 ratio means that rope must be pulled 5x the distance the weight needs to move
One lunar day, the time between sunrises if you lived on the moon is approximately
28 days
Nellie pulls a 10kg wagon with a constant horizontal force of 30N. If there are NO other horizontal forces, what is the wagon's acceleration?
3 m/s^2 F=ma
Rocket initially at rest accelerates at a rate of 50 m/s^2 for 1 min., its speed will be:
3,000 m/s a= change in v/ t
What F is required to push a 10kg box up a 10m frictionless incline to a height of 3m?
30 N use Work= change in PE equation PE= mgh to find PE in J plug in Work (J) to W=Fd to find F for 10m distance.
500 N parachutist opens his chute and experiences an air resistance of 800 N. The net force on the parachutist is
300 N upward (Fnet= W-R)
What is the acceleration of a car that starts from rest and 5 secs later reaches a speed of 20 m/s?
4 m/s^2 using a= (change in v/ time)
Two asteroids in space have gravitational force b/n them of 100N. If the distance b/n the asteroids is increase by factor of 5, what will the gravitational force between the asteroids become?
4N Use F= G (m1 x m2)/r^2 to calculate
The BF on a 50 ton ship is equal to
50 tons
Joshua is attracted toward Earth by a 500-N gravitational force. Earth is attracted toward Joshua with a force of:
500 N (same amt of gravitational force applied between us and Earth)
At one instant an object in FREE FALL is moving downward at 50 m/s. One second later its speed is:
60 m/s Each second in free fall increases speed by 10 m/s.
Sandbag is motionless in outer space. A second sandbag with 3 times the mass moving at 12 m/s collides with it. They stick together and move at a speed of
9 m/s Use m1v1 + m2v2= (m1 + m2) Vf
The min. amt of water required to float a 100 ton ship is
A cap full
When a solid is changed to a liquid, the solid
Absorbs energy Phase change graph Moving up in E on the graph--> E is absorbed
Airplane flight best illustrates
Bernoulli's principle: fluids have less pressure when moving fast ex: curve ball, airplane wings, wind blowing over roof or umbrella
In a vacuum, an object has no
Buoyant force
A cannon recoils while firing a cannonball. The speed of the cannon's recoil is relatively small because the
Cannon has much more mass than the cannonball. Recoil is small which means the cannon has high inertia (reluctant to move) Mass increases, speed decreases, inertia increases Greater mass means greater inertia & also greater momentum
Impulse=
Change in momentum
An arch bridge made of stone is held together by which type of stress?
Compression
Suppose a particle is being accelerated through space by a 10N force. Suddenly the particle encounters a second force of 10N in the opp direction of the first force. The particle with BOTH forces acting on it:
Continues at the speed it had when it encountered the second force Newton's 2nd Law Forces react to equal a 0 Net Force
A temp diff of 10 degrees C is also equal to a temp diff of 10 on the:
Kelvin scale Both C and K based on 100 pt scale b/n freezing & boiling pts. If it were comparing to F, each degree of F is worth more (larger) and would not equal C or K change.
Using the data of Tycho Brahe, Kepler was able to determine that planets orbit the sun in
Elliptical paths
If work is done on something, the following is changed
Energy
Truck is moving at constant velocity. Inside the storage compartment, a rock is dropped from the midpoint of the ceiling and strikes the floor below. The rock hits the floor
Exactly below the midpoint of the ceiling Because truck & rock continue to move at same velocity forward.
When at 4 degrees C is heated it expands. When water at 4 degrees C is cooled, it
Expands 4 C is the expansion point of water. Water will expand when heated or cooled.
Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to:
Follow a straight-line path (linear path)
Two identical golf carts move at different speeds. The faster cart has twice the speed and therefore has
Four times the KE KE= 1/2mv^2 KE given in Joules
A coconut and feather fall from a tree through the air to the ground. The force of air resistance is:
Greater on the coconut. More mass= more air resistance
Lobsters live on the bottom of the ocean. The density of a lobster is
Greater than the density of sea water. ** If object is more dense than surrounding fluid, it will sink **
Clerk can lift packages 1m vertically or can roll them up a 2m long ramp to the same elevation. With the ramp, the applied force required is about:
Half as much How much work to get up to top? W= change in E= change in PE= mgh Find W in joules then plug into W=Fd to calculate F for each situation
The distance a freely falling bowling ball falls each sec:
INCREASES x= 1/2gt^2 shows that when h and v are originally 0 that after 1s the bowling ball would have fallen 5m then 20m at 2s. Distance does NOT increase at intervals of 10m.
Holding a helium balloon. Which experiences greater BF, the floating balloon or instructor?
Instructor Which displaces more air? Has more object volume?
Two blocks of identical size are placed in a pool. One block is made of Styrofoam and the other out of lead. After the blocks are released and allowed to settle, the buoyant force will be greatest on the:
Lead block It displaces larger Volume of water. BF= volume of water displaced
The Bernoulli principle states that the pressure of a fast moving fluid, relative to a slow moving fluid is
Less Fast moving fluids have lower pressure
Merry-go round questions:
Linear speed faster on outside Rotational speed slower on outside As diameter/ radius increase, rotational speed decreases and linear speed increases v=rw
A substance that heats up relatively quickly has a
Low specific heat Specific heat applies to heat transfer versus conductivity that deals with touch This means it takes a low level of heat for substance to heat up
One of the main reasons one can walk barefoot on red-hot coals of WOOD without burning their feet has to do with
Low thermal conductivity of the coals Coals have a high temperature but are not conducting the heat well into touch of human feet
Near the top of a mountain, water in an open pot boils at
Lower temperature than at sea level Less pressure on water from atmosphere so less E needed to overcome liquid pressure
Student holds a barometer as she rides an elevator to the top of a tall building. As she rises in the building she notices that the level of her barometer
Lowers Barometer: measures weight of atmosphere Atmosphere weighs less above the student as she rises up!
Standing on a bathroom scale, a student sees their weight as 110 pounds. If all the air was removed from the room the bathroom scales would read
More than 110 pounds Air resistance removed from the room--> weight increases Buoyancy F of air removed in vacuum--> slightly larger F applied to scale
Cart A is within a defined system. Later, Cart B enters the system and collides with Cart A. Was momentum conserved the entire time?
NO Beginning and ending momentum will NOT be equal because there was an external force applied to the system. If you want no external forces, both cart A and cart B would have to be defined as a single system.
A large truck will always have more inertia than a roller skate. Will it always have more momentum?
NO Inertia is resistance to change which increases with mass (Momentum= inertia x velocity) So if truck is moving at low velocity and roller skate at very high velocity, th roller skate could have more momentum
Horses with the greatest linear speed on a merrygoround are located
Near the OUTSIDE Faster linear speed on outside of circle
Which of the following does NOT cause tides on Earth?
Neptune, Sun, and Moon all cause tides
When a rocket ship gaining speed in outer space runs out of fuel, it
No longer gains speed; continues at current speed
Buoyancy Force on object SUBMERGED in liquid depends on...
Object volume + Density of liquid
If a strong wind from the WEST breaks a window in the North wall of a house, most of the glass will fall:
Outside the house. Lower pressure of FAST moving air will suck it OUT
Pascals Law
Pressure change in confined, incompressible fluid is transmitted throughout liquid so that same change occurs everywhere
Ocean tides are primarily caused by our moon. This is because the moon
Pulls harder on the side of the Earth facing the moon than the backside
Wrapping a hot potato in aluminum foil significantly reduces the rate at which it loses E by:
Radiation- electromagnetic waves from aluminum foil
When a gas is changed to liquid, the gas
Releases E Moving to lower E
A ring and a disk both at rest roll down a hill together. Which accelerates SLOWER?
Ring. the disk would roll faster because its center of mass is within the object.
If its easier to balance a bat with hand on handle than end then
Rotational inertia is higher
Compared to the mass of a certain obj on Earth, the mass of the same object on the moon is:
SAME Weight changes on moon, mass does NOT change.
Car traveling at 100 km/h strikes a bug and splatters it. The force of impact is:
SAME for both car and bug Newton's 3rd law: For every action there is an equal & opp reaction F of Bug (small m, big a)= F of Car (big m, little a)
Two life preservers have identical volumes, but one is filled with Styrofoam while the other is filled with sand. When the two preservers are fully submerged, the BF is greater on the one filled with
Same on each as long as their volumes are the same. Both would displace same amt of H20 if volumes are the same. Not dependent on mass.
When you stand at rest with your left foot on one bathroom scale and your right foot on similar scale, each of the scales will
Show readings that when added equal your weight
The chef at the infamous Fattening Tower of Pizza tosses a spinning disk of uncooked pizza dough into the air. The disk becomes wider during its flight, while its rotational speed;
Slows Equation: v=rw As radius increases, rotational speed decreases. As radius increases, linear speed increases.
Two students are riding next to each other on merrygoround. Student A is closer to the CENTER of rotation than Student B. The student with the highest linear speed is:
Student B. Linear speed greatest on outside of circle. Rotational (RPM) speed same on outside and center
A large block of Styrofoam and small block of lead each measure 10 N when placed on a scale. Which has MORE MASS?
Styrofoam block Not sure why?
Which exerts the greatest force on the Earth?
Sun
A 5 kg clump of clay traveling at 10m/s hits and sticks to a wall. A 5kg super bounce ball traveling at 10 m/s hits and bounces off a wall. Which exerted the greater force on the wall?
Super bounce ball Has greater impulse Impulse= change in momentum & Impulse= Ft
A ball rolling down an incline has its maximum PE at:
TOP of incline. Max KE at bottom.
The white-hot sparks that strike skin from sparkler don't harm you because
The energy per molecule is high, but little E is transferred because of the few molecules in the spark.
2 blocks of identical size are submerged. One is heavy & other is light. Which has greater BF?
They both experience the same, because BF depends only on density of liquid & obj volume. Not on mass of object.
A student sitting halfway between center and edge of merrygoround. Merrygoround is spinning on frictioness bearings and has constant rotational velocity. If the student wants to slow the rotational velocity, they should crawl:
Towards the outside If the mass moves further from the point of rotation, the angular velocity will reduce (mVr = mvR)
Relative to initial height, an object raised twice as high has a gravitational PE
Twice as much PE=mgh mass remains the same
If you place a pipe over the end of a wrench when trying to rotate a bolt, effectively making the wrench handle 2x long, you'll multiply the torque by:
Two Torque is same equation as Work. T= Fd (d represents radius distance which is two times greater)
Tidal forces in general are the result of
Unequal forces acting on different parts of the body -Distance from moon effecting tides on diff parts of Earth (pulling stronger on side facing moon)
A completely submerged object always displaces its own
Volume of fluid
A submerged object will always displace its
Volume of water
Boyles Law
When temp & mass are constant--> pressure and velocity are inversely proportional
A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is
Zero Newton's 1st law: object will stay in motion unless acted upon by an outside force Friction & air resistance are neglected here!!
If an object of constant mass experiences a constant net force, it will have a constant
acceleration Use F=ma formula
Toss a baseball bat into the air and it wobbles about its:
center of mass
