Exam 2 Questions
It takes 40 J to push a large box 4m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box?
10N
Why does the vertical component of velocity for a projectile change with time, whereas the horizontal component does not?
Because of the force of gravity, which acts on a downward (vertical) force. The horizontal component has no such force and it remains unchaged
Emily holds a banana of mass m over the edge of a bridge of height h. She drops the banana and it falls to the river below. Use conservation of energy to show that the speed of the banana just before hitting the water is v = sq. rt. of 2gh
KE = PE 1/2mv = mgh
The reason the moon does not crash into the Earth is that the
Moon has a sufficient tangential speed
A 1-kg ball dropped from a height of 2m rebounds only 1.5m after hitting the ground. The amount of energy converted to heat is about
More than 2J (PE= ugh)
What is a mixture?
Not chemically bonded atoms (Air)
Atomic Number
Number of protons/electrons in a neutral atom
What is a projectile?
Projectile motion is a form of motion in which an object or particle (called a projectile) is thrown near the earth's surface, and it moves along a curved path under the action of gravity only
A ball is thrown horizontally from a cliff at a speed of 10 m/s. You predict that its speed 1 second later will be slightly greater than 14 m/s. Your friends say it will be 10 m/s. Show who is correct.
Sq. Rt. of 196
Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60km /hr?
The 60 km/hr car
What is the work energy principle?
The change in the kinetic energy of an object is equal to the net work done on the object.
No force due to Earth's gravity is acting on astronauts inside the orbiting space shuttle. This statement is
always false
Inside a free falling elevator, there would be no
apparent weight for you
A car travels in a circle with constant speed. The net force on the car is
directed toward the center of the curve
According to Newton, doubling the distance between two interacting objects will do what to the gravitational force between them?
divides by 4 the gravitational force between them
The chemical properties of matter come mostly from its
electrons
The atomic number of an element matches the number of
electrons of a neutral atom
Lever is a simple machine consisting of a rigid rod pivoted at a fixed point called
fulcrum
The gravitational field best suited for humans living in a outer space colony is
g
When carbon and oxygen atoms combine, energy is
given off by the reaction
According to Newton, the greater the masses of interacting objects, the
greater the gravitational force between them
positrons
have the same mass as an electron but are positively charged
The direction of a gravitational field is
in the same direction as the gravitational attraction
If the radius of the Earth somehow decreased with no change in mass, your weight would
increase
When the distance between two stars decreases by half, the force between them
increases to four times as much
What is centripetal force and what affects it?
the force pulling you towards the center of a circle. Acceleration, Linear speed and radius affect the centripetal force
Consider two planets in space that gravitationally attract each other. If the masses of both planets are doubled, and the distance between them is also doubled, Then the force between them is
the same
A carnival has a Ferris wheel where the seats are located halfway between the center and outside rim. If you were at the outside rim, your angular speed while riding on this ferris wheel would be
the same and your tangential speed more
A ring, a disk, and a solid sphere begin rolling down a hill together. The one to reach the bottom first is the (assume all the objects have the same mass)
the sphere
An asteroid exerts a 400-N gravitational force on a nearby spacecraft. This force is directed
towards the asteroid
If you find that twice as much work is needed to perform a task but it takes twice as much time, the amount of power required is
unchanged
A 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 (v^2 second speed) / (v^2 first speed) = X * 20m
The power required to exert 1 N force, over a distance of 1m in 1 second is
1W
What is the electronic configuration of Manganese (Mn) atom with atomic number 25
1s(2 )2s(2) 2p(6) 3s(2) 3p(6) 4s(2) 3d(5)
Suppose the circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second when you are riding the bicycle, then your speed will be
2 m/s
What change in kinetic energy does an airplane experience on takeoff if it is moved a distance of 500 m by a sustained net force of 5000N?
2.5 x 10^6 J
Suppose you're on a Ferris wheel at a carnival, seated 10m from the Ferris wheel's axis. If you make a complete rotation each minute, your linear speed is
2.8m/ min
A stone is thrown horizontally from the top of a cliff. Two seconds after it has left your hand, its vertical distance below the top of the cliff is
20m
Atomic Mass
Average mass of all isotopes
A 150gm ball at the end of a string is revolving uniformly in a horizontal circle of radius 0.6m. The ball makes 4 revolutions in a second. What is its centripetal acceleration?
378.61 m/s^2
A projectile is fired into the air at an angle of 50 degrees with the ground and lands on a target that is at the same level at which the projectile started. At what other angle will it land on the same target?
40 degrees
a TV set is pushed a distance of 200m with a force of 2N. How much work is done on the set?
400J
An asteroid exerts a 360-N gravitational force on a nearby spacecraft. If the spacecraft moves to a position three times as far from the center of the asteroid, the force will be
40N
What is the force of gravity on a 500-newton woman standing on the Earth's surface?
500N
a 2-kg mass is held 4m above the ground. what is the approximate potential energy of the mass with respect to the ground?
80J
A projectile is fired at an angle of 45 degrees with initial velocity of 140 km/ hr. What is the velocity of the projectile at the top of it''s path?
99 km/ hr
An object is dropped and freely falls to the ground with an acceleration of 1 g. If it is thrown upward at an angle instead, what will be its acceleration?
Acceleration will still be 1g downward
What is a compound?
Chemically bonded atoms (H2O)
An object is placed exactly halfway between the Earth and moon. The object will fall toward the
Earth
What is conservation of energy for machine?
Energy transforms without net loss or net gain in the operation .
A rock is thrown upward with 20 m/s at 65 degrees with respect to the horizontal. As it rises, neglecting air drag, what will be its horizontal and vertical components?
Vertical = 18.13 m/s Horizontal = 8.45 m/s
A ball player wishes to determine pitching speed by throwing a ball horizontally form an elevation of 7m above the ground. The player sees the ball land 21m down range. What is the player's pitching speed?
VoX = 17.8 m/s
Atoms of the same element with different numbers of neutrons are called
isotopes
If the sun somehow became twice as massive, your weight as normally measured here on Earth would
not change
Horses that move with the fastest linear speed on a merry-go-round are located
on the outer edge
Half way to the center of a planet of uniform density, your weight compared to that at the surface would be
one-half
In an electrically neutral atom, the number of protons in the nucleus is balanced by an equal number of
orbital electrons
The trajectory of a projectile is known as a
parabola
The force of gravity acts on all apples on a apple tree. Some apples are twice as far from the ground as others. These twice-as-high apples, for the same mass have
practically the same weight
What is circular motion?
refers to motion around the physical or hypothetical circumference of a circle
What is rotational motion?
refers to objects rotating upon an axis of an object
A torque acting on an object tends to produce
rotation