When stopping a car on an icy or wet road … or a dry road, for that matter …
is it better to push the brake pedal hard enough to lock the wheels and make them slide or
to push gently so that the wheels continue to roll? What is the point behind
"anti-lock disk brakes"?
What is the angle between vectors and
and if · = - AB?
Consider the drawing below. In terms of m1, m2 and g, find the
acceleration of each block in the system. Assume there is no friction anywhere in the
system. Check your solution with limiting cases.
Now, for the system considered in the question above, assume there is friction between m1
and the table surface. What is the minimum value of m s
that will keep the blocks from moving? Why do I ask for m s
and not m k?
You move a big box up a frictionless inclined plane. Does the inclined plane save you
work? If not, what is the advantage of using an inclined plane for lifting the box?
A 30 g bullet initially traveling 500 m/s penetrates 12 cm into a wooden block. What
average force does it exert on the block?
A car is stopped by a constant friction force that is independent of the car's speed. By
what factor is the stopping distance changed if the car's initial speed is doubled? Hint:
think about work and energy conservation.
A traffic engineer claims that traffic lights timed so motorists can travel long
distances between stops will improve air quality in a city. Do you believe this? Why or
why not?
If time, do:
A bucket of mass 7.25 kg hangs in a well at the end of a rope. The rope passes over a
frictionless pulley at the top of the well, and you pull horizontally on the end of the
rope to raise the bucket slowly a distance of 6.00 m. a) How much work do you do on the
bucket in pulling it up? b) How much work is done by the gravitational force acting on the
bucket? c) What is the total work done on the bucket?
In the above question, why does it specify that you raise the bucket slowly? Suppose you
raised it quickly with varying acceleration? How would this change the problem?
and
and 
if 