Fundamentals 9 Flashcards
About how much of a circle is a radian? (Your answer may not reference π).
about 1/6 of a circle, or about 60 degrees. (To two digits, that’d be 57 degrees.)
What is the formula for rotational inertia of a point object?
MR^2
A ball is launched vertically off of a table, 70 cm above the floor. The ball reaches a maximum height of 160 cm above the floor, then falls to the floor. What is the magnitude of the ball’s displacement between the table and the floor?
70 cm. (Displacement is the distance from the beginning to the end of a motion, without regard for what happens in between.)
A ball has 100 J of gravitational potential energy relative to the ground when it is dropped from rest from a high cliff. The ball has 60 J of kinetic energy right before hitting the ground. How much work was done by air resistance during the ball’s fall?
40 J. (The energy bar chart will show that 100 J of gravitational energy plus the work done by air resistance equals the 60 J of kinetic energy at the ground. Leaving 40 J of work done by air.)
Cart A, of mass 1 kg, moves left with speed 1 m/s. What is the magnitude and direction of cart A’s momentum?
1 Ns, left. (Momentum is mv; the direction of momentum is the same as the direction of motion.)
Cart A, of mass 1 kg, moves left with speed 1 m/s. Cart B, of mass 1 kg, moves right with speed 1 m/s. What is the total kinetic energy of the two-cart system?
1 J. (Kinetic energy does not have direction; so all kinetic energies add together. Each cart has 0.5 J of kinetic energy.)
A car moves east at 30 m/s. Ten seconds later, the car moves east at 10 m/s. What is the magnitude and direction of the car’s acceleration?
2 m/s/s, west. (Acceleration is the change in speed every second. The car changes speed by 20 m/s over 10 seconds, so that’s a change of 2 m/s every 1 second. And when an object slows down, its acceleration is opposite the direction of motion.)
How do you determine an object’s speed from a velocity-time graph?
look at the vertical axis
Define torque.
force times lever arm.
I attach a 20 g mass to a spring, set the spring in harmonic motion, and measure its period. The mass is determined using period = 2πroot(m/k). Did I determine gravitational mass or inertial mass?
inertial. (The equation for the period of a spring does not involve gravitational field or the universal gravitation constant.)
