Physics Test 2
The rest energy of a 60 kg person is:
5.4x10^18 J
The relativistic momentum of a 1000 kg car moving at 0.95 times the speed of light is:
9.13x10^11 kg m/s
Which of the following would cause a household fan to stall?
The blades are too sharply angled for the speed the fan rotates; The fan is rotating too fast
Why are failures in dams more likely to occur closer to the bottom of the dam?
Water pressure is higher at the bottom.
Fluids have viscosity because
the atoms and molecules within the fluid interact with each other, producing internal frictional forces.
You are riding in a hot air balloon. You have not used the burner for some time and the balloon begins to sink. Assuming that no air is allowed to leave or enter the balloon,
the average density of the balloon became greater than the surrounding air and the buoyant force on the balloon became less than its weight.
The speed at which a car must move so that its relativistic energy is three times its rest energy is
√(8/9)times the speed of light
What mass has a rest energy of 100J?
1.1x10^-15 kg
Atmospheric pressure is about 100000 Pa. At what depth in water does this pressure double?
10 m
The relativistic energy of a 1000 kg car moving at 0.95 times the speed of light is:
2.9x10^20 J
The onset of turbulent flow happens for a Reynolds number of about
2300
Water weighs about 10 N per liter on Earth. A 4.0 liter ball is pushed underwater on the space shuttle, where gravity was 1/10 that on Earth. What is the buoyant force on the ball?
4 N
Water weighs about 10 N per liter. A 4.0 liter ball is pushed underwater. What is the buoyant force on the ball?
40 N
What is the gravitational force that two 100 kg persons exert on each other when standing 1m apart?
6.672x10^-7 N
How far apart would two 100 kg persons need to be so that the force they exert on each other is equal to 1N? You can assume they are point masses, having mass but no size.
8.17x10^-4 m
The diameter of a pipe is tripled while the pressure difference across the pipe remains the same. The volume flow rate of the pipe increases by a factor of
81
Why will a rolled - up ball of aluminum foil float in water but solid aluminum will sink?
Due to the air inside, the average density of the ball is lower than water.
When a fluid is in steady - state flow and its path bends, the pressure on the outside of the bend is always
Higher than the pressure on the inside of the bend.
At what place in or near the jet engine is gas moving the fastest relative to the flying airplane?
In the plume of exhaust gas flowing out of the engine's outlet duct.
When a fish hovers over the bottom of a lake, what forces act on it, and what is the net force?
Lift and weight, for a net force zero.
Suppose you are spending your weekend on roller skates trying to get momentum from somewhere. Which of the following will give you momentum in the north direction?
Throwing your keys southward.
When moving, a bicycle is in a state of dynamic equilibrium due to which of the following?
both gyroscopic effects and the shape of the fork
A curve ball's path bends to the right as it flies toward home plate because it is experiencing an aerodynamic force to its right. One reason why the ball is experiencing this aerodynamic force is that the ball is spinning and that spin
causes the air to flow more rapidly around the right side of the ball than around the left side of the ball.
Aerodynamic forces consist of
drag and lift.
As the Reynolds number decreases,
flow is going from being viscous dominated to inertia dominated and therefore turbulent.
At various times in the news it has been reported that certain vehicles are susceptible to rolling over. The physical mechanism that is responsible for rollovers is
frictional torques from the road on the vehicle about its center of mass, which is below the rider
The maximum speed a rocket can achieve is
greater than the speed of its exhaust plume but less than the speed of light.
Suppose you have two containers with liquid in them. One has a density of 760 kg/m3 and the other has a density of 910 kg /m3. If an object floats in one container and sinks in the other, the density of the object
has a value between 760 kg/m^3 and 910 kg/m^3.
Flowing honey is less likely to become turbulent than flowing water because
honey's large viscosity favors laminar flow.
An object is in stable equilibrium only when
its total potential energy rises whenever it reorients.
Compared to planets close to the sun, and based upon Kepler's third law of planetary motion, the length of the year of planets farther out from the sun are
larger.
You stop for a cappuccino at a coffee shop and notice that the tiny white bubbles of steamed milk remain on the surface of the coffee. These air-filled bubbles stay where they are, rather than descending into the coffee or rising into the air, because they are
less dense than the coffee but more dense than the air above the coffee.
A curve ball in baseball curves because of
lift forces.
A fan can be used to circulate air around a room. The pressure at the inlet side of the fan is
more than the pressure at the outlet side.
If a golf ball were smooth rather than dimpled, it would
not travel as far after being hit by a golf club.
Gravity creates
pressure gradients in fluids.
Rockets receive their forward propulsion through
pushing against the exhaust.
The top surface of a calm, smoothly flowing stream is always at atmospheric pressure. As water in this stream runs into a tree stump and slows almost to a stop, the water's top surface
shifts upward slightly above the normal stream level
Suppose you are operating a fan and it is stalling. One thing that would not prevent stalling would be to
speed up the fan
A three - wheeler is
statically stable and dynamically unstable.
A top is
statically unstable and dynamically stable
A motorcycle is
statically unstable and dynamically stable.
In studying many martial arts, it is necessary to practice efficient and safe postures. One important concept related to how one should stand is that the feet should be reasonably far apart, because
the base of support is wider, thus stabilizing the person.
Why does fuzz on a tennis ball help it travel farther when hit?
the fuzz "trips" the boundary layer, causing turbulence everywhere around the ball.
You are holding two identical-looking balloons, one filled with air and one filled with water. You drop these two balloons from a very tall bridge and notice that the water-filled balloon hits the ground first because its terminal velocity is larger. The terminal velocity of the water balloon is larger than that of air balloon because
the larger force of gravity on the water balloon must be balanced by a larger drag force, which occurs at a higher speed
A squirt gun is a simple type of water pump in which a plunger attached to the trigger forces water out of a nozzle and across the room. When you squeeze the trigger of the gun, water squirts out of the nozzle because
the pressure inside the gun is higher than atmospheric pressure
When driving down a level smooth road, your car tires flatten at the bottom and they nicely support the weight of your car. However when you run over a small pointed rock the tire is punctured and fails. The rock is able to puncture the tire because
the small surface area of the rock times the pressure in the tire is not enough force to support the car. Thus, the tire fails.
For an object that sinks in a fluid,
the weight of fluid displaced is less than its weight
For an object that sinks in a fluid,
the weight of fluid displaced is less than its weight.
For an object that is floating on a fluid,
the weight of the fluid displaced equals the object's weight.
For an object that is neutrally buoyant in a fluid,
the weight of the fluid displaced equals the object's weight.
Astronauts in the space shuttle feel weightless because
they are in a constant state of free - fall.
The reason fast-moving water makes noise is
turbulence
When you pour honey into a bowl, it flows smoothly. If you did the same with water, it would splash. These different behaviors occur because honey's high
viscosity keeps it flowing smoothly while water's low viscosity allows inertia to break its flow into many separate pieces
The four things that affect the amount of water flowing through a hose are
water viscosity, hose length, inlet and outlet pressures and hose diameter.
In a popular classroom demonstration, a cotton ball is placed in the bottom of a strong test tube. A plunger fits inside the tube and it makes an air - tight seal. It is then pushed down very rapidly, and the cotton flashes and burns. This happens because
when the air was compressed its temperature increased.
