Fundamentals 13 Flashcards
A rope pulls with a tension of 100 N at an angle of 20 degrees above the positive x axis. Which has greater magnitude - the x component of this tension, or the y component of this tension?
the x-component. (The x-component is 100 N cos 20, while the y-component is 100 N sin 20.)
A solid cylinder of mass M and radius R rolls down an incline. Is its rotational inertia about its center greater than, less than, or equal to MR^2?
less. (The rotational inertia would be MR^2 if all the mass were located a distance R from the axis of rotation. A solid cylinder has most of its mass less than R from the center! So its rotational inertia is less than MR^2.)
A ball is thrown at an angle above the horizontal. When it is just about to hit the ground, what is the magnitude of the horizontal component of its acceleration?
zero
An object moves in a circle at constant speed. Describe the direction of the unbalanced force on the object.
towards the center of the circle
An object has mass 100 kg. I take this object to Mars, where the free-fall acceleration is 4/10 that on earth. What is the weight of this object on Mars?
400 N. (On earth, the weight would be 1000 N. On Mars, the weight would be 4/10 of that. The mass is still 100 kg.)
Is work a vector or scalar quantity? (That is, does work have a direction, or not have a direction?)
scalar, no direction
Planet A of mass M and planet B of mass 4M are separated by a distance X. What is the magnitude and direction of the force of planet A on planet B?
G(M)(4M)/x^2, direction is to the left in the diagram, toward planet A. (Other permutations of this equation are fine, like 4GM^2/x^2, etc.)
What is the equation for spring potential energy?
Us = (1/2)kx^2
Two carts on a horizontal frictionless track collide with each other and stick together, though they keep moving. What forms of energy does the two-cart system possess after the collision? Take the gravitational potential energy to be zero.
kinetic energy and internal energy. (The collision is inelastic, so the energy cannot be all kinetic after collision.)
In one experiment, a felt-covered 1 kg block slides on an aluminum track. The block slides to rest. In a second experiment, an additional 2 kg is placed on top of the block, and the block slides to rest again from the same initial speed. How does the coefficient of friction experienced by the block change in the second experiment?
it is unchanged. (The coefficient of friction depends only on the surfaces in contact.)
