Physics final Exam
A ball of mass m1=20 kg hit another ball of mass m2=10 kg at a velocity of 100 m/s head-on. What would be the velocity of the second ball after the collision (assuming a pure elastic collision)? -100 m/s -200 m/s -2000 m/s -2 m/s
200 m/s
A force of 3 N is applied to an object, producing and acceleration of 10 m/s2. If the mass of the object is doubled and we apply the same 3 N, what acceleration would you expect? -50 m/s2 -5 m/s2 -10 m/s2 -20 m/s2
5 m/s2
A person mass 78 kg on Earth and now goes to Mars which has half gravity compare to Earth. What the person mass will be on mars?
78 kg
What is the definition of inelastic collision? -A collision where object hit each other head-on and then they move apart -A pool table example collision -A collision where object shares momentum and after collision -they depart each other -A collision where the objects remain entangled after the collision
A collision where the objects remain entangled after the collision
Which of the following examples is an example of Newton's third law? -A inflated balloon with an open end and its motion due to the air flowing out -A hammer hitting a nail - All of the others answer are viable options -The lift off of a rocket
All of the others answer are viable options
A block is place on an inclined plane as in figure below. Which of the four arrows indicates the Force of gravity acting on the block?
C
A block is placed on top of an inclined plane as shown in figure below. Which of the marked arrows indicates the component of the force of gravity that DOES NOT contribute to the motion of the block and it is compensated by the support force?
D
Which Newton's laws can be demonstrated observing the effect of a boxer hitting a punching bag with a naked fist?Explain it in 20 words and bring another example of the same law.
Newton's third law, when a boxer hits a punching bag, his fists hits the bag sending a force to the punching bag, the bag then responds by sending a force back to the boxer, therefore, stopping its motion. Another example of Newton's third law is when a swimmer finishes a lap and pushes off the wall with their feet, the swimmer sends a force against the wall and the wall responds by equaling the force of the swimmers kick, sending the swimmer forward in an accelerating motion.
What phenomenon is involved in the functioning of the car brakes? Explain in at least 20 words.
Pascals principle, it's the phenomenon where the liquid in a container undergoes pressure change its transmitted without loss to every part of the container. And how it works with car brakes and lifting cars is because the pressure is equal to the force divided by the area. So the pressure on the small tube of the car brakes will send enough pressure and force to stop the car.
Which of the following represents Newton's third law?
Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.
Describe in your own words what happens to the bare feet of the guy walking on the hot charcoal. Describe the phenomenon that occurs between the charcoal and the skin of the feet and the key physical quantities involved. (at least 20 words)
Your Answer: Coal is a bad conductor of heat so therefore it would take a longer time to burn your feet, so the faster you move over the coals the less heat would transfer from the coals to your feet.
A cart is moving on an inclined plane in a vaccum environment. Knowing that the cart and the surface of the plan are corrugated, what type of friction is present?
sliding friction
We define the acceleration of an object as...
the variation in velocity over a period of time
In a hydraulic press, piston A has an area of 10 cm2 and the other end piston B has an area of 1 m2. If we apply 10 N force on piston A, how much force results on piston B? -1 N -1000 N -10000 N -10 N
-1 N
What volume of water corresponds 0.01 L -10 cm3 -100 cm3 -1000 cm2 -0.01 cm3
-10 cm3
What is the pressure exerted by a 10kg mass over a 1 m2 surface (remember 1 Pa = 1 N/m2)? -10 Pa -1 Pa -200 Pa -100 Pa
-100 Pa
What is the work done by a machine that applies a force of 40 N in order to move an object of 30 m? -120 J -1200 Kg -1200 J -240 J⋅m
-1200J
If the torque applied by a wrench on a bolt is 340 N m. and the length of the wrench is 0.2 m, what is the force applied? -200 N -1700 N -350 N -20 N
-1700 N
How many electron can be placed in the first orbital? -9 -2 -4 -3
-2
The helium atom has 2 protons. How many electrons can be placed in the closest shell? -1 -6 -4 -2
-2
What force is exerted on a 150 cm2 surface if the total pressure is 150 Pa? -225 N -2.25 N -22.5 N -150 N
-2.25 N
If you put a rock of 10 Kg in a glass completely filled with water that weighs 20 N, what is the final weight of the glass with the rock? -20 N -100 N -80 N -120 N
-20 N
If a truck going 100 km/h with a mass of 400 kg hits a car at rest (zero speed). What is the velocity of the car after the impact if the car weight is 200kg? -500 km/h -200 km/h -100 km/h -400 km/h
-200 km/h
Applying Pascal principle to a hydraulic press with a weight of 20 kg over an area of 10 m2, what is the force acting on the other side of the press knowing that the area is 100 m2? See example here (disregard the numbers in it): -2000 N -200 N -20 N -10 N
-2000 N
What is the torque of a force of 20 N applied with a lever of 10m? -100 N m -200 N/m -200 N m -200 N
-200N m
A ball of mass m1=20 kg hit another ball of mass m2=10 kg at a velocity of 100 m/s head-on. What would be the velocity of the second ball after the collision (assuming a pure elastic collision)? -100 m/s -200 m/s -2 m/s -2000 m/s
-200m/s
What is the gravitational potential energy of a person whose weight is 70kg on top of a flight of stairs 30 m high? -700 J -2100 Nm -21 kJ -2100 J
-21 kJ
What is the impulse produced by a boxer when she punches a bag with a force of 230N and the impact last 0.1s? -23 kg m/s -23 N -35 kg m/s -2300 kg m/s
-23 kg m/s
What is the power of a machine that produces 2340 J of work in 10 second? -234 kWatt -234 kWh -2340 Watt -234 Watt
-234 Watt
What is the kinetic energy of a bowling ball (1.5 kg) when is launched with a speed of 2 m/s?3 -1.5 J -3 J -2 J -6 j
-3 J
What is the pressure of a 120 N force over a squared surface of 20 cm side? -3000 N/m2 -300 N/m -3000 N/m -300 N/m2
-3000 N/m2
What is the Force applied on your head (area equal to 300 cm2) knowing that the pressure is 101,325 N/m2? -3039.75 N -30.3975 N -303975 N -50 N
-3039.75 N
What is the kinetic energy of a 500 kg car that goes freely downhill at a speed of 45 km/h when it reaches the bottom of the hill, knowing that it started at a height of 50m ? -3.9 kJ -390 J -39 kJ -3900 J
-39kJ
An object is tossed from a 30m tall building vertically with a velocity of 10m/s. It reached a height of 10m high and then falls straight back on the ground at the base of the building. What was its velocity when it reached the ground (remember that velocity is a vector quantity)? -10 m/s -20 m/s -30 m/s -40 m/s
-40 m/s
What is the velocity of a baseball when thrown with a momentum of 23 kg m/s, considering that the weight of the ball is 0.5 kg? -460 m/s -30 mph -230 m/s -46 m/s
-46 m/s
You are on top of a 10 m hill. What is your potential energy if your mass is 60 kg? -6 kJ -600 N -600 J -60 k
-6 kJ
What is the work done by a force of 30 N moving an object in absence of friction for 200 cm? -6000 N -60 J -60 N cm -6000 N m
-60 J
A track of mass 300 kg is moving at a speed of 80 km/h. The driver falls asleep and accidentally drives into the following car which is going at 65 km/h. If the collision is inelastic and the mass of the car is 120kg, what is the final velocity of the track+car system? -79.3 km/h -145 km/h -85 km/h -80 km/h
-79.3 km/h
What is the definition of a "mixture"? -A substance that is mixed together due to its electric properties -A substance that is mixed together due to temperature -A substance that is mixed together without chemically bonding -A substance that is chemically bound
-A substance that is mixed together without chemically bonding
What is the definition of a "mixture"? -A substance that is mixed together without chemically bonding -A substance that is mixed together due to its electric properties -A substance that is chemically bound -A substance that is mixed together due to temperature
-A substance that is mixed together without chemically bonding
How can you make a boat to float? -Using material less dense than water -All of the above -Making sure that the when submerged the boat received enough force due to Archimede's principle -Making sure the weight of the displaced water is equal to the weight of the boat
-All of the above
Which of the following collision examples are perfect elastic collisions? -a train wagon hitting another one transferring all its momentum to the second one -All of the above -A tennis racket hitting a tennis ball -two billiard balls hitting each other and going separate ways
-All of the above
What is the main cause of brownian motion of particles? -All of the others -the density of the particles -the mass of the particles -the temperature of the particles
-All of the others
What is the main cause of brownian motion of particles? -the temperature of the particles -the mass of the particles -the density of the particles -All of the others
-All of the others
Which of the following is an elastic collision? -two billiard balls hitting each others -All of the others -A air hockey puck hitting the side of the field -A baseball hitting a bat
-All of the others
Which of the following is an example of Newton's third law in action? -A hammer hitting a nail -A boxer punching a bag -All of the others -A basketball player jumping off the ground
-All of the others
Why air balloons float in the air? -Because they are filled with gas less dense than air -Because they are filled with gas heavier than air -Because they are always filled with hot gas -None of the above
-Because they are filled with gas less dense than air
A liquid boils at sea-level at a temperature of 120 C. What you expect to happen to the boiling temperature if the liquid is taken on a mountain at 4000 feet from sea-level? -Boiling temperature is less than 120 C -Boiling temperature is greater than 120 C -Boiling temperature is still 120 C
-Boiling temperature is less than 120 C
What shape are the orbits of the planets around the Sun? -Circles -Ellipses -Squares -Triangles
-Ellipses
How a refrigerator can provide cool temperature inside? -Having the heat transfer to the outside via a "heat pump " -Maintaining ice in the back of the fridge -Through cold air flowing inside -Through continuously pumping icy air from the freezer
-Having the heat transfer to the outside via a "heat pump "
How much the Volume of liquid in a piston changes, when is compressed by a pressure of 200,000 Pa? -It does not change -it becomes 1/200000 higher -none of the above -it becomes 1/200000 smaller
-It does not change
Evaluate the following statement: "A body in total mechanical equilibrium has net force and net toque equal to zero" -It is true only if the object is not in linear motion with constant speed -It is True -It is not true -It is true only if the object is in linear motion with constant speed
-It is True
What is the definition of "center of mass"? -It is the geometric center of the object -It is the point in the object that correspond to the heavier part of the object -It is the point in the object that correspond to the lighter part of the object -It is the average position of all the masses that make up the object
-It is the average position of all the masses that make up the object
How can you describe the molecules in liquid substances compared to the ones in solids? -colder -More closely bound -More attached to each other -More loosely bound
-More loosely bound
If a force acting on a cart does not produce motion is there "work" done by the force on the cart? -Only if there is energy transferred -Yes -No
-No
Is momentum conserved only in elastic collisions? -Yes -Yes, because the velocity remain the same -No -Yes, because there is no exchange of momentum
-No
Is momentum conserved only in elastic collisions? -Yes, because there is no exchange of momentum -No -Yes -Yes, because the velocity remain the same
-No
If object A has a larger rotational inertia than object B, when both objects roll down an inclined plane, which of the two will get to the bottom earlier? -Object A -They will arrive at the same time -Object B
-Object B
What principle is behind the hydraulic press? -Archimede's principle -Pascal's principle -Newton's 3rd law -Torricelli's principle
-Pascal's principle
What does "Conservation of Momentum" mean? -That in absence of external forces the momentum of a system remains unchanged -That in absence of an external force the momentum is zero -That in absence of external forces the momentum of a system decreases uniformly -That in absence of external forces the momentum of a system increases uniformly
-That in absence of external forces the momentum of a system remains unchanged
If you push a crate horizontally, but the crate does not move. What can you say about the force of friction? -That is smaller to the force you apply to move the crate -The force of friction is very small -That is equal or larger than the force you apply to move the crate -That there is no friction
-That is equal or larger than the force you apply to move the crate
How can you define buoyancy? -The apparent loss of weight experienced by object only when they are totally submerged in a liquid -The effect of atmospheric pressure on an object submerged in water -The apparent loss of weight experienced by object submerged in a liquid -The apparent increase in weight an object experiences when is submerged in water
-The apparent loss of weight experienced by object submerged in a liquid
What is the definition of Work done by a force moving an object? -The product of the Force times the distance the object travels as result of the force -The amount of force applied by a certain time -The force times the square of the distance -The force divided the distance
-The product of the Force times the distance the object travels as result of the force
What is the main characteristic that determine the phase of a substance (liquid, solid, or gas)? -The temperature -the hight from the ground -the mass -the force of gravity
-The temperature
What is the "internal energy" of a substance? -Just the amount of kinetic energy -Just the amount of thermal energy -Just the amount of vibrational energy of the molecules that make up that substance -The total energy inside it
-The total energy inside it
What is the "internal energy" of a substance? -Just the amount of vibrational energy of the molecules that make up that substance -The total energy inside it -Just the amount of kinetic energy -Just the amount of thermal energy
-The total energy inside it
Which of the following phenomena is an example of convection ? -The transfer of heat within different layers of the atmosphere -The emission from the Sun on your skin -The heating of a metal bar on a flame -The heat transfer from your hand to a cold drink
-The transfer of heat within different layers of the atmosphere
What is the definition of "escape velocity"? -The velocity needed for an object to fully escape the gravitational pull of a planet -The final velocity of a rocket after escaping the gravitational pull of mars -The velocity needed to arrive to the Moon -The velocity of a rocket to overcome air resistance force
-The velocity needed for an object to fully escape the gravitational pull of a planet
What does it happen to most substances when heated ? -They change chemical composition -Their temperature diminishes -They reduce their volume -They expand
-They expand
Why the tightrope walker has a long stick on his hands? -To increase her rotational inertia -To increase her linear inertia -To increase her linear momentum -To increase her angular momentum
-To increase her rotational inertia
Gravitational force that attracts us towards Earth is the same that attracts Earth towards us. -False -True
-True
If you have a sealed container filled with water. how its volume will change if the pressure on the liquid increases 10 times higher than atmospheric pressure? -Volume will remain unchanged -Volume will be 10 times higher -Volume will be 10 times smaller -Volume will only change of 1 %
-Volume will remain unchanged
Pascal's principle affirms that...(complete) -a change in pressure at any point in an enclosed fluid gets transmitted equally to all points in the fluid -pressure exerted on the top of a enclosed fluid gets transmitted equally only to the bottom of the container -a pressure applied on a side of a fluid in a container results in twice as much pressure on the other side of the container -a pressure applied on a side of a fluid in a container results in half as much pressure on the other side of the container
-a change in pressure at any point in an enclosed fluid gets transmitted equally to all points in the fluid
The direction of the Force due to the pressure of the liquid on an object is... (complete) -always perpendicular to the surface of the object -always parallel to the surface of the object -always at 45 degrees to the surface of the object -always perpendicular to the surface of the liquid
-always perpendicular to the surface of the object
Complete the sentence: "The net momentum before a collision and the net momentum after the collision... -are the same -are not the same in inelastic collisions -are never the same -are the same only in elastic collisions
-are the same
The rotational speed of an object in uniform rotational motion is defined as... -the linear velocity of an object at the edge of the circular path -the linear velocity of an object at half the distance between the center of the circular path and the edge -the time it takes to do 10 revolution -as the number of rotation per unit time
-as the number of rotation per unit time
The rotational speed of an object in uniform rotational motion is defined as... -the time it takes to do 10 revolution -the linear velocity of an object at the edge of the circular path -as the number of rotation per unit time -the linear velocity of an object at half the distance between the center of the circular path and the edge
-as the number of rotation per unit time
Why does the vertical component of velocity for a projectile change with time, whereas the horizontal component of velocity doesn't change? -because gravitational pull only applies to the vertical component -because gravitational pull only applies to the horizontal component -because the mass of the object is higher in the vertical component -because the the horizontal velocity is always greater than the vertical component
-because gravitational pull only applies to the vertical component
If we put the filled cylinder and the ring of the same mass and sizes on a slope, why the filled cylinder goes down faster? -because it has larger rotational inertia -because resistance is different -because it has smaller rotational inertia -because on the gravity acts differently
-because it has smaller rotational inertia
Why is water a bad thermal conductor? -because of the amount of oxygen in the water molecules -it is not, it is a good thermal conductor -because its high heat capacity -because its low heat capacity
-because its high heat capacity
Why it was important that Torricelli barometer had "vaccum" on one end? -because otherwise there would be "air pressure" inside the tube and we could not measure air pressure outside -because air contains other elements that would change the chemical composition of the liquid -because otherwise mercury would not be visible -because otherwise mercury would fill up the tube entirely due to capillarity
-because otherwise there would be "air pressure" inside the tube and we could not measure air pressure outside
What is the unit measurement of heat? -Farenheit -Centigrade -calorie -Kelvin
-calorie
What is the name of the process that makes a gas becoming a liquid? -condensation -convection -sublimation -freezing
-condensation
At what temperature water reaches the highest desity? -0 degrees F -four degrees C -four degrees F -0 degrees C
-four degrees C
What happen to the internal energy of a substance when transitions from liquid to solid? -it decreases -it doubles -it increases with the temperature -It triples
-it decreases
On planet A the escape velocity is 30 m/s. Planet B twice more massive than planet A. What can we say about the escape velocity of planet B? -it is the same -it is around 2 m/s -it is 15 m/s -it is 60 m/s
-it is 60 m/s
How can you make a sheet of aluminum to float ? -modeling it such that the weight of the water displaced when immersed in water is equal to the weight of the whole sheet -modeling it such that the volume is the smallest possible (like a small cube or sphere) -modeling it such that the shape resemble the one of a boat -modeling it such that the shape resemble the one of a plane
-modeling it such that the weight of the water displaced when immersed in water is equal to the weight of the whole sheet
What is the definition of momentum? -mv2 -m/v -mv -1/2mv2
-mv
What is the definition of momentum? -1/2mv2 -mv2 -mv -m/v
-mv
A person on the escalator is slowly going from a height of 12 m to the ground floor of a building. What is her potential energy when it reaches 8m from the starting point? -one third of the original kinetic energy -it is equal to its kinetic energy -two thirds of the original one -one third of the original one
-one third of the original one
When you spin on an axis (like while ice-skating) your rotational inertia is larger is... -put your arms above your head -jump -kneel down -open your arms
-open your arms
Between the following radiation waves which one has the longest wavelength? -radio -infrared -X-ray -Gamma-ray
-radio
The centripetal force is stronger.... (complete the sentence) -the smaller the velocity of the object that rotates is -the smaller the mass is -the closer you are to the center of rotation -the further you are to the center of rotation
-the closer you are to the center of rotation
What is the smallest particle in an atom? -the protons -the nucleus -the electrons -the neutrons
-the electrons
The frequency of a radiation wave is connected to... -the chemical content of the object that emits that wave -the mass of an object that emits that radiation -the energy carried by the wave -the pressure inside the object that emits that wave
-the energy carried by the wave
What is the cause of surface tension? -the temperature of the fluid -the molecular bond of the fluid molecules -the density of the fluid -the weight of the fluid
-the molecular bond of the fluid molecules
What is the cause of surface tension? -the weight of the fluid -the density of the fluid -the molecular bond of the fluid molecules -the temperature of the fluid
-the molecular bond of the fluid molecules
The temperature of two different substances may rise differently if given the same amount of heat because... -their respective heat capacity -the gravitational potential energy -Their shapes -the kinetic energy of their molecules
-their respective heat capacity
The temperature of two different substances may rise differently if given the same amount of heat because... -the kinetic energy of their molecules -their respective heat capacity -Their shapes -the gravitational potential energy
-their respective heat capacity
How much pressure there is on Mars, compare to atmospheric pressure, if a mercury barometer measures 380 mm of mercury? -0.5 atmospheres -2 atmospheres -3 atmospheres -the same
0.5 atmospheres
