In the absence of air resistance, a ball of mass m is tossed upward to reach a height of 20 m. At the 10-m position, half way up, the net force on the ball is
When you drop a ball it accelerates downward at 9.8 m/s2. If you instead throw it downward, then its acceleration immediately after leaving your hand, assuming no air resistance, is
A heavy rock and a light rock in free fall (zero air resistance) have the same acceleration. The reason the heavy rock doesn't have a greater acceleration is that the
ratio of force to mass is the same.
A cannonball is fired horizontally at 10 m/s from a cliff. Its speed one second after being fired is about
Relative to the ground, an airplane gains speed when it encounters wind from behind, and loses speed when it encounters wind head on. When it encounters wind at a right angle to the direction it is
A karate chop delivers a force of 3000 N to a board that breaks. The force that the board exerts on the hand during this event is
A math book and a physics book are tied together with a length of string. With the string taut, one
book is pushed off the edge of a table. As it falls, the other book is dragged horizontally across the
table surface. With no friction, acceleration of the books is
a value between 0 and g
When an increase in speed doubles the momentum of a moving body, its kinetic energy
more than doubles
When an increase in speed doubles the kinetic energy of a moving body, its momentum
increases but less than doubles
When a spinning system contracts in the absence of an external torque, its rotational speed increases
and its angular momentum
Consider a ball rolling down an inclined plane. The normal force on the ball (the force perpendicular
to the plane).
is less than mass/gravity always
Consider a ball rolling in a horizontal circular path on the inside surface of a cone. The normal force on
is greater than mg always
When a ball at rest hangs by a single vertical string, tension in the string is mg. If the ball is made to
move in a horizontal circle so that the string describes a cone, string tension
is greater than mg always
Imagine you're standing on the surface of a shrinking planet. If it shrinks to one-tenth its original
diameter with no change in mass, on the shrunken surface you'd weigh
100 times as much
The fact that the Moon always shows its same face to Earth is evidence that the Moon rotates about its
axis about once per
The Moon is most responsible for Earth's tides. Which pulls more strongly on the Earth and its oceans?
A spacecraft on its way from Earth to the Moon is pulled equally by Earth and Moon when it is
closer to the moons surface
The mass of a classical atom comes mostly from its ____ ; and its volume from its ______.
Consider a block of wood floating on water. If you push down on the top of the block until it's
completely submerged, the buoyant force on it
An inflated balloon with a heavy rock tied to it submerges in water. As the balloon sinks deeper and
deeper, the buoyant force acting on it
The "greenhouse gases" that contribute to global warming absorb
more infrared radiation than visible.
In a mixture of hydrogen, oxygen, and nitrogen gases at a given temperature, the molecules having
the greatest average speed are those of
The electrical force of attraction between an electron and a proton is greater on the
Neither; both are the same.
Immediately after two separated charged particles are released from rest, both increase in speed. The
particles therefore have
either the same or opposite signs of charge.
Compared with the current in the white-hot filament of a common lamp, the current in the connecting
A capacitor loses half its charge every second. If after five seconds its charge is q, what was its initial
All of the following are electromagnetic waves EXCEPT
None is outside the family; all are electromagnetic waves. radio waves, light waves microwaves, x rays
You swing to and fro on a playground swing. If you stand rather than sit, the time for a to-and-fro
ompared with the sound you hear from the siren of a stationary fire engine, the sound you hear
when it approaches you has an increased
Your friend states that under all conditions, any radio wave travels faster than any sound wave. You
agree with your friend
To view your full-face image in a steamy mirror, compared to the height of your face, the minimum
height of the patch to wipe away is
Light reflecting from a smooth surface undergoes a change in
None of these
Which of these changes when light refracts in passing from one medium to another?
both of these
wavelength and speed
When the color yellow is seen on your TV screen, the phosphors being activated on the screen are
red and green
Astrophysicists are able to identify the elements in the outer layers of a star by studying its
Any atom that emits an alpha particle or beta particle
becomes an atom of a different element, always.
Suppose the number of neutrons in a reactor that is starting up doubles each minute, reaching one
billion neutrons in 10 minutes. When did the number of neutrons reach half a billion?
When a uranium nucleus undergoes fission, the energy released is primarily in the form of
kinetic energy of fission fragments.
When a fusion reaction converts a pair of hydrogen isotopes to an alpha particle and a neutron, most
of the energy released is in the form of
kinetic energy of the neutron.
Because there is an upper limit on the speed of particles, there is also an upper limit on
none of these
Relativistic equations for time dilation, length contraction, and relativistic momentum and energy
hold true at