Physics Things to Know Flashcards
How do you determine instantaneous velocity from a position-time graph?
Slope at a given time
How do you determine instantaneous velocity from a velocity-time graph?
Value at the given time
A block is in equilibrium. What is the Newton’s third law force pair to the normal force?
The force the block puts on the surface
What is the same for resistors in parallel?
Voltage drop
What is the equivalent resistance of two 50 ohm resistors in parallel?
25 ohms
What is the more common word for the “magnitude of the velocity vector?”
Speed
Write the impulse-momentum theorem.
FΔt = Δp
State the formula for the angular momentum of a point object.
L = mrv
State the formula for the angular momentum of an extended object, like a disk or a sphere.
L = Iω
A 1 kg object moves at 2 m/s. Can this object collide and experience MORE that 2 N᛫s of impulse?
Yes
What property of a circuit involved the number of electrons passing a position in 1 s?
Current
John exerts a 4 N force to the left on a cart; Peggy exerts a 3 N force to the right on the cart. Which way is the cart moving?
Can’t be determined
What physical property of a wave relates to the energy carried by the wave?
Amplitude
Under what conditions can you set up forces equal to down forces?
Equilibrium (a = 0)
Equation for energy stored by a spring.
PE = 1/2 kx²
A 1 kg wooden crate and a 2 kg wooden crate are separately dragged across the floor. What quantity must be the same for both crates?
Friction (μ)
Write the equation for the electrical force between two point charges.
F = (kq1q2) / r²
Two massive objects each have a net negative charge. When they are placed near one another, do they attract or repel electrostatically?
Repel
Write the equation for the period of a pendulum.
T = 2π √(l/g)
Write two versions of the equation for electrical power.
P = IV P = I²R P = V² / R
Wire 1 is 20 cm long and made out of aluminum. Wire 2 is 40 cm long, of the same cross sectional area, and also made out of aluminum. How many times larger is the resistivity of wire 2 compared to wire 1?
Resistivity is the same.
The amplitude of an antinode on a standing wave on a string is 2 cm; the period of the wave is 4 s. What is the average speed of the string at the position of the antinode?
2 cm/s
Draw a representation of the longest-wavelength standing wave that can exist in a pipe which is open at one end and closed at the other end.
Half a wave
A planet’s orbit about a sun is elliptical. Consider a system consisting of just the planet. Is the planet’s angular momentum about the sun conserved?
No
An object is hung from a spring scale, which reads 2.0 N. Dividing by 10, it’s determined that the object’s mass is 0.2 kg. Which kind of mass was determined?
Gravitational Mass
An object is attached to a horizontal spring, compressing the spring by 0.15 m. A second object, twice as massive as the first, compressed the same spring by 0.15 m. By how much has the potential energy of the spring-object system changed?
None
1/2kx²
A 10 N block is on a surface is which the static friction coefficient is 0.2. The force of friction on the block is 1 N. How is this possible?
F (static friction) ≤ μ (static) F (normal)
Identify the error: “Ball A was thrown at a speed of 30 m/s at an angle of 20° above the horizontal. Since its acceleration is 10 m/s², its speed after 3 s will be zero.”
Acceleration is in the vertical direction. Only Ball A will have a non-zero speed.
Why is it wrong to say “the kinetic energy of the hanging block is downward?”
Energy is secular with no direction
Define an “elastic” collision.
No loss of kinetic energy; object bounces perfectly
