Quizzics Theoretical
A ball is thrown straight up. At the highest point of its motion:
Which of the following are zero: velocity, acceleration, force, kinetic energy?
Only velocity and kinetic energy are zero.
Gravity still acts, so force and acceleration are nonzero.
A bicycle starts from rest and accelerates uniformly at 2 m/s² for 5 s.
What is its final speed?
10 m/s
Estimate the combined weight of all the students in your school
160K kg
anything close is fine
How long does it take light to travel from the sun to Earth
8:20 minutes
8 minutes is fine
A block rests on a frictionless table. A string attached to the block passes over a pulley at the table’s edge and supports a hanging mass. The system is released from rest.
If the string suddenly snaps while the system is moving, what happens to the block on the table immediately after?
The block continues moving at constant velocity.
Once the string snaps, there is no horizontal force on the block. By Newton’s First Law, it keeps its current velocity.
A runner runs 100 m east at 10 m/s, then 100 m west at 5 m/s.
What is the runner’s average speed for the whole trip?
6.7 m/s (approximately)
How many packets are needed to measure a single line of M&Ms to a distance of 100m?
223 packets
Anything close is fine
What is the speed of light
3*10^8 m/s
Two people stand on frictionless ice, initially at rest, holding a rope between them. One person pulls the rope toward themselves.
Does the center of mass of the two-person system move?
All forces are internal. With no external horizontal force, the center of mass remains fixed, even though both people move.
A 20 kg crate rests on a horizontal floor. The coefficient of static friction is 0.4. A horizontal force of 50 N is applied.
What is the subsequent acceleration of the crate?
0 the crate doesn't move.
Estimate the number of phones actively being used worldwide right now.
~2 billion phones
anything close is fine
what is earth's radius? in km
6,378 km
anything close to that is fine
A uniform rod of length L lies on a table. One end of the rod is heated so that its density near that end decreases linearly from "p" to "0.8p" over a distance L/4. The rest of the rod remains uniform.
Where is the center of mass relative to the midpoint of the rod?
The center of mass shifts away from the heated end.
The heated section loses mass density, so less mass is concentrated near that end. Since the rod is otherwise uniform, the balance point must move toward the cooler, denser side.
Two trains move on parallel tracks.
Train A moves east at 20 m/s
Train B moves east at 30 m/s
A passenger on Train A throws a ball straight north at 10 m/s relative to Train A.
What are the components of the velocity of the ball as seen by a passenger on Train B
Ground frame:
East: 20 m/s
North: 10 m/s
How many commercial airplanes are in the air globally?
~10,000
anything close is fine
what is the sun's radius? in km
695.7 km
anything close to 700 km is fine
A circular conducting loop lies flat on a table. A bar magnet is held directly above the center of the loop, with its north pole facing downward toward the loop. The magnet is released and falls straight down through the center of the loop.
As the magnet falls through the loop, does it fall faster than, slower than, or at the same rate as it would without the loop?
The magnet falls slower than it would without the loop.
A laser emits 1 mW of green light (wavelength =500 nm). Calculate how many photons are emitted per second.
2.5*10^15 photons per second
How long would it take to drive to the moon (if you could!)
160 days
accept any close answer
what is the diameter of the observable universe? in light years
93B light years
anything close to 100B light years is fine