Mechanics | Relativity Answers

For a biological sample in a 1.0-m radius centrifuge to have a centripetal
acceleration of 25g, (g = 9.8 m/s2) its speed must be:
A. 11 m/s
B. 16 m/s
C. 50 m/s
D. 122 m/s
E. 245 m/s

The mass differs from the weight in that:
A. all objects have weight but some do not have mass
B. weight is a force and mass is not
C. the mass of an object is always more than its weight
D. mass can be expressed only in the metric system
E. there is no difference

A Newton is the force:
A. of gravity on 1kg
B. of gravity on 1 g body
C. that gives a 1 g body an acceleration of 1m/s2
D. that gives 1 kg body an acceleration of 1 m/s2
E. that gives a body of 1 kg mass an acceleration of 9.8 m/s2

Which of the following quantities is not a vector
A. Mass
B. Displacement
C. Weight
D. Acceleration
E. Force

The SI units of force is numerically equal to the …….. , when the force is applied
to it.
A. The velocity of a standard kilogram
B. The speed of a standard kilogram
C. The velocity of the object
D. The acceleration of the standard kilogram
E. The acceleration of any object

A stone is tied to a 0.5-m string and whirled at a constant speed of 4.0m/s in a
vertical circle. Its acceleration at top of the circular path is:
A. 9.8 m/s2, up
B. 9.8 m/s2, down
C. 8.0 m/s2, up
D. 32 m/s2, down
E. 32 m/s2, up

a) A dentistry student is running with a constant acceleration until she reached a max
speed of 5m/s. If she suddenly sees a wall 20 m in front of her, how long will it
take her to come to a complete stop just before she reaches the wall, what was her
acceleration?
b) If the same student decided to check what is behind the wall by stepping 5 meters
back and throwing a rock so that just clears the 2-m high wall. What should be the
initial velocity (magnitude and direction) by which she must throw the rock, so
that it just clears the wall at its max height of trajectory?

A ball is thrown vertically upward from the surface of the earth. Consider the
following quantities: (1) the speed of the ball; (2) the velocity of the ball; (3) the
acceleration of the ball. Which of these is (are) zero when the ball has reached the
maximum height?

A racecar, traveling at constant speed, makes one lap around a circular track of radius r
in a time t. Determine the magnitude of the average velocity of the car for one complete
lap.

In which one of the following situations does the car have a westward acceleration?
(a) The car travels westward at constant speed.
(b) The car travels eastward and speeds up.
(c) The car travels westward and slows down.
(d) The car travels eastward and slows down.
(e) The car starts from rest and moves toward the east.