Physics test 2
Projectile curves as a result of these 2 components.
-Constant motion horizontally -Accelerated motion vertically
What speed does an object need to travel at in order to escape the gravitational influence of earth?
11.2 kilometers per second from Earth's surface
For equal launching speeds, the same range is obtained from two different projection angles—a pair that add up to ________.
90 degrees
What is Pascal's principle?
A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid. Ex. Hydraulic press F1A1 = F2A2
What is an inelastic collision?
A collision whereupon colliding objects become tangled or coupled together, generating heat. (Inelastic collisions are often sticky.) -Conservation of momentum YES -Conservation of Energy NO
What is an elastic collision?
A collision whereupon objects collide without permanent deformation or the generation of heat. (The elastic balls bounce!) -Conservation of momentum YES -Conservation of Energy YES
If a projectile is fired straight up at a speed of 10 m/s, neglecting air resistance, the time it takes to reach the top of its path is A) 1 s. B) 2 s. C) 10 s. D) not enough information
A- 1 s
A stone is thrown horizontally from the top of a cliff. One second after leaving your hand it drops a vertical distance of A) 5 m. B) 10 m. C) 15 m
A- 5 m
If the volume of an object were to double with no change in mass, its density would A) be half. B) double. C) unchanged
A- be half
Acceleration is greatest for a satellite in elliptical orbit when it is A) closest to Earth. B) farthest from Earth. C) same at both places
A- closest to the earth
As a swimmer dives deeper and deeper, strictly speaking, the volume of water displaced by the swimmer actually A) decreases. B) increases. C) remains unchanged but pressure on her increases. D) none of the above
A- decreases
Very importantly, a hydraulic press can multiply A) forces. B) pressures. C) energy. D) all of the above E) none of the above
A- forces
Suppose you stand on a weighing scale and all of a sudden the atmosphere vanishes. The reading on the scale would A) increase. B) decrease. C) remain the same.
A- increase
When a dish falls, will the change in momentum be less if it lands on a carpet than if it lands on a hard floor? (Careful!) A. No, both are the same. B. Yes, less if it lands on the carpet. C. No, less if it lands on a hard floor. D. No, more if it lands on a hard floor.
A. No, both are the same
A glass vase that falls on the floor will be less likely to break if the floor is carpeted. This is because A. force of impact will be less because time of impact will be longer. B. Impulse will be less because of the softer surface C. both of these D. neither of these
A. force of impact will be less because time of impact will be longer.
Standing on a skateboard, you toss a ball horizontally away from you. The mass of the ball is one tenth your mass. Compared with the speed you give the ball, your ideal recoil speed will be A. one tenth as much B. the same C. ten times as much D. one hundred times as much
A. one tenth as much
If the mass of a cart full of groceries decreases to half and its speed doubles, the momentum of the cart A. remains unchanged B. is doubled C. is quadrupled D. decreases
A. remains unchanged
A big fish swims upon and swallows a small fish at rest. After lunch, the momentum of the big fish is A. the same as before B. less than before C. more than before D. zero
A. the same as before
What is a projectile?
Any object that moves through the air or through space under the influence of gravity.
When an object is partly or wholly immersed in a liquid, it is buoyed up A) by a force equal to its own weight. B) by a force equal to the weight of liquid displaced. C) and floats because of Archimedes' principle. D) but sinks. E) none of the above
B) by a force equal to the weight of liquid displaced.
Two equal-sized buckets are filled to the top with water. One of the buckets has a piece of wood floating in it, making its total weight A) less than the weight of the other bucket. B) equal to the weight of the other bucket. C) more than the weight of the other bucket.
B) equal to the weight of the other bucket.
An egg is placed at the bottom of a bowl filled with water. Salt is slowly added to the water until the egg rises and floats. From this experiment, we conclude that A) egg-shell calcium is repelled by sodium chloride. B) the density of salt water exceeds the density of the egg. C) buoyant force does not always acts upward. D) salt sinks to the bottom. E) none of the above
B) the density of salt water exceeds the density of the egg.
What is the buoyant force acting on a 10-ton ship floating in the ocean? A) less than 10 tons B) 10 tons C) more than 10 tons D) depends on density of seawater
B- 10 tons
The density of air at room temperature is about 1.2 grams/cm3. Estimate the mass of air inside an average automobile. A) 2 grams B) 2 kg C) 20 kg D) 200 kg E) 2000 kg
B- 2 kg
In the vacuum of outer space, there is no A) gravity. B) atmospheric pressure. C) Both
B- atmospheric pressure
3) A rock is thrown upward at 50° with respect to the horizontal. As it rises, its horizontal component of velocity A) increases. B) remains unchanged. C) decreases
B- remains unchanged
Consider two tubes filled with water at the same height, one with fresh water and the other tube with salt water. The pressure is greater at the bottom of the tube with A) fresh water. B) salt water. C) both the same D) depends on whether the tubes have the same cross-sectional area.
B- salt water
Newton discovered A) gravity. B) that gravity is universal. C) Neither
B- that gravity is universal
If a pressure of 20 kPa is applied to one piston in a simple hydraulic device, the pressure on a piston of larger area will be A) less than 20 kPa. B) the same 20 kPa. C) more than 20 kPa. D) all of the above E) none of the above
B- the same 20 kPa
When a chocolate bar is cut in half, its density is A) halved. B) unchanged. C) doubled.
B- unchanged
When the speed of an object is doubled, its momentum A. remains unchanged in accord with the conservation of momentum. B. doubles. C. quadruples. D. decreases.
B. doubles
Freight Car A is moving toward identical Freight Car B that is at rest. When they collide, both freight cars couple together. Compared with the initial speed of Freight Car A, the speed of the coupled freight cars is Conservation of Momentum CHECK YOUR NEIGHBOR A. the same. B. half. C. twice. D. None of the above.
B. half After the collision, the mass of the moving freight cars has doubled.
A cannonball shot from a cannon with a long barrel will emerge with greater speed, because the cannonball receives a greater A. average force. B. impulse. C. Both of the above. D. Neither of the above.
B. impulse
When the force that produces an impulse acts for twice as much time, the impulse is A. not changed. B. increased by two times. C. increased by four times. D. decreased by half.
B. increased by two times
The impulse-momentum relationship is a direct result of Newton's A. first law B. second law C. third law D. law of gravity
B. second law
A very massive object A and a less massive object B move toward each other under the influence of gravity. Which force, if either, is greater? A) the force on A B) the force on B C) both forces are the same
C- both forces are the same
A rock is thrown upward at 50° with respect to the horizontal. As it rises, its vertical component of velocity A) increases. B) remains unchanged. C) decreases
C- decreases
Water pressure at the bottom of a lake depends on the A) weight of water in the lake. B) surface area of the lake. C) depth of the lake. D) all of the above
C- depth of the lake
A ball is thrown upwards and caught when it returns to the same point. Neglecting air resistance, the speed with which it is caught is A) more than its initial speed. B) less than its initial speed. C) the same as its initial speed.
C- the same as its initial speed
A 1-kg ball has the same speed as a 10-kg ball. Compared with the 1-kg ball, the 10-kg ball has A. One tenth the momentum B. the same momentum C. 10 times as much momentum D. 100 times as much momentum
C. 10 times as much momentum
If your speeding car slams into a haystack and comes to rest, how will the FORCE that acts on it compare to slamming into a brick wall and coming to rest? A. More B. Less C. Same
C. Same
If your speeding car slams into a haystack and comes to rest, how will the IMPULSE that acts on it compare to slamming into a brick wall and coming to rest? A. More B. Less C. Same
C. same
A tennis ball is launched from a launching machine. Compared with the amount of impulse on each ball, the amount of impulse on the machine is A. larger B. smaller C. the same D. not enough information is given to say
C. the same
Two iron balls, one twice the mass of the other, are dropped from rest from the top of a one story building. Compared with the lighter ball, the twice as heavy ball when hitting the ground has A. half the momentum B. the same momentum C. twice the momentum D. four times the momentum
C. twice the momentum
A common 5-L metal can will float in air if it is A) evacuated of air. B) filled with a very large amount of helium. C) thrown high enough into the air. D) Nonsense! Unless the can and displaced air weigh the same, the can can't float in air.
D) Nonsense! Unless the can and displaced air weigh the same, the can can't float in air.
A projectile is launched at an angle of 15° above the horizontal and lands downrange. With no air resistance, what other projection angle for the same speed would produce the same downrange distance? A) 30° B) 45° C) 50° D) 75° E) 90°
D- 75
A satellite in an elliptical orbit travels at constant A) velocity. B) speed. C) acceleration. D) all the above E) none of the above
D- none of these
A fast-moving car hitting a haystack or hitting a cement wall produces vastly different results. Both experience A. the same change in momentum. B. the same impulse. C. the same force. D. A and B.
D. A and B
A moving object has A. momentum. B. energy. C. speed. D. All of the above
D. All of the above
When you jump from an elevated position to the ground below, the force you experience when landing depends on A. the jumping height B. the softness or hardness of the ground C. how much your knees bend D. All of the above
D. All of the above
Skelly the skater travels at high speed and needs a certain amount of force to stop him. More stopping force will be needed if he has A. more mass B. more momentum C. less stopping distance D. all of these
D. all of these
Your friend says the impulse equals momentum. You disagree and say the friend is missing an important word, which is A. inertia B. acceleration C. time D. change
D. change
Formula for density
Density= mass/volume
Escape velocity is escape speed when _________ is involved.
Direction
The reason a life jacket helps you float is that A) the jacket causes you to weigh less. B) the jacket has the same density as an average human. C) the jacket repels water. D) if you sink, the jacket sinks. E) the combined density of you and the jacket is less than your density alone.
E) the combined density of you and the jacket is less than your density alone.
Consider two planets in space that gravitationally attract each other. If the masses of both planets are doubled, and the distance between them doesn't change, then the force between them is A) one-quarter. B) half as much. C) twice as much. D) four times as much. E) none of the above
E- none of the above
A collision in which colliding objects rebound without lasting deformation or the generation of heat
Elastic collision
What is conservation of energy?
Energy can not be created or destroyed, it can only be transformed from one form to another.
Formula for Inverse square law
F= G (M1+M2/ d2) For two bodies, this force is directly proportional to the product of their masses and inversely proportional to the square of the distance separating them
True of false: Impulse and momentum are two words for the same concept.
False
True or false: Impulses are smaller when bouncing occurs.
False
True or false: Padding is put in the dashboard of a car to reduce momentum during a collision.
False
Which of the following equations best illustrates the usefulness of automobile air bags? A. a=F/m B. Ft= change in mv C. d= 1/2 gt^2 D. d=vt
Ft= change in mv
In an elliptical orbit, when the satellite is closest to earth does it gain or lose speed?
Gain speed
How do you determine the amount of pressure in a gas?
Gas pressure is a measure of the amount of force, exerted by the motion of molecules bouncing around, per area that a gas exerts against containing walls.
If fast Freddy doubles his running speed, what else doubles?
His momentum
Formula for impulse
I = F x t
The product of the force acting on an object and the time during which it acts. In an interaction, they are equal and opposite.
Impulse
What is the Impulse-momentum relationship?
Impulse is equal to the change in the momentum of the object that the impulse acts on. Ft = change in mv
Impulse is equal to the change in the momentum of the object that the impulse acts on.
Impulse-momentum relationship
A collision in which the colliding objects become distorted, generate heat, and possibly join together.
Inelastic collision
In a circular orbit, the speed of the satellite _____________.
Is constant
When no external net force acts on an object or a system of objects, no change of momentum takes place. Hence, the momentum before an event involving only internal forces is equal to the momentum after the event.
Law of conservation of momentum
Formula for liquid pressure
Liquid pressure = weight density x depth
formula for momentum
Momentum= mv
Formula for momentum
P= mv
What do you call a curved path of a projectile?
Parabola
Formula for pressure
Pressure= force/Area
What do you call fast moving projectiles?
Satellites
How do you determine the buoyancy of a liquid?
The amount equals the weight of water displaced.
What is energy?
The capacity to bring a change in the state or form of an object.
What is escape speed?
The initial speed that an object must reach to escape gravitational influence of Earth.
Which has more momentum, a 100-kg lineman running at 10 km/h or a 75-kg quarterback running at 12 km/h?
The lineman mass x velocity
What is atmospheric pressure?
The pressure exerted against bodies immersed in the atmosphere resulting from the weight of air pressing down from above.
What is Bernoulli's principle?
The pressure in a fluid moving steadily without friction or outside energy input decreases when the fluid velocity increases. ( Where the speed of fluid increases, internal pressure in fluid decreases)
What is Boyle's Law?
The product of pressure and volume is a constant for a given mass of confined gas regardless of changes in either pressure or volume individually, so long as the temperature remains unchanged. P1V1 = P2V2
What is impulse?
The product of the force acting on an object and the time during which it acts. I an interaction, they will be equal and opposite.
What is momentum?
The product of the mass of an object and it's velocity.
What is power?
The time rate of doing work
What is the work energy theorem?
The work done on an object is equal to the energy gained by the object. Can be a change in PE or KE. Work= change in energy
True or false: When a net force acts on a system, the momentum of the system will change.
True
True or false: When the net force on a system is zero, no change in the system's momentum occurs.
True
Newton discovered that gravity is ____________.
Universal
In an elliptical orbit, the speed of the satellite __________.
Varies.
What is Law of conservation of momentum?
When no external net force acts on an object or a system of objects, no change of momentum takes place. Hence, the momentum before an event involving only internal forces is equal to the momentum after the event. mv (before event)= mv (after event)
Formula for work
Work= force x distance
What is Archimedes principle?
an immersed body (completely or partially) is buoyed up by a force equal to the weight of the fluid it displaces applies to all fluids (gases and liquids).
Formula for impulse
impulse= Ft (force x time)
The product of the mass of an object and its velocity
momentum
