Download Test 1 Sample Questions

PHS 112
Test 1 Review
Chapters 1-4
If velocity and speed are both measures of how fast something moves, then how are they different?
Velocity includes a direction vector that speed does not have.
Can an object be moving and at equilibrium? What does “net force” mean?
Moving or stationary the net force is zero at equilibrium. Net force refers to the sum of all
the forces. Force is a vector quantity so forces often cancel each other.
The amount of air resistance depends on an object’s size and an object’s speed.
Air resistance is a type of friction. This force is more commonly associated with one solid object sliding across
another.
Do our bodies attract the earth toward us? If so, how does the force of our bodies pulling on the earth compare with
the force of the earth pulling on us?
We attract the earth to us with a force equal to the force of the earth attracting us.
Define inertia.
Resistance to change in motion/velocity. Speeding up; slowing down; turning.
In the absence of air resistance, will two objects with very different masses fall at the same speed? Are they being
accelerated by the same amount of force?
They fall at the same speed. The more massive object requires more force to accelerate as
fast as the less massive object (Law of Acceleration), and is pulled by more force, because
the force of gravity is proportional to the mass.
Object A falls on a table and doesn’t bounce. Object B has the same mass and falls the same distance to the table
but bounces. Do they hit the table with the same amount of force? Do they hit the table with the same amount of
impulse?
Impulse = Ft = Δmv Without knowing the time (t) they take to stop or bounce, we cannot
know the force. The object that bounces has a greater impulse because the change in
velocity (v) is greater.
If the acceleration of gravity on the moon is 1.6m/s2, how fast is an object falling after one second? Two seconds?
How far will an object fall in one second? Two seconds?
1.6m/s; 3.2m/s; 0.8m (average speed in 1st second = 0.8m/s); 3.2m (average speed in 2nd
second = 2.4m/s; 0.8m + 2.4m = 3.2m)
The moon’s radius is a little more than ¼ that of earth. The moon’s mass is about 1/80th that of earth.
Approximately how do each of these two differences between the earth and moon increase or decrease the
gravitation on the surface of the moon compared to earth?
mass1 × mass2
Decreasing the mass decreases the value of the numerator in this
distance 2
proportion, which decreases the force of gravity. Decreasing the radius decreases the
distance between the objects. Squaring the decrease in distance makes the denominator
F∼
even smaller, which increases force. The decrease in gravity caused by the much smaller
mass has a greater effect than the increase in gravity caused by the decrease in distance
squared. The force of gravity on the moon is 1/6th that on earth.
Two men are working on a scaffold at right. The scaffold weighs 400N, the
left man weighs 300N, and the right man weighs 400N. The cable on the left
end of the scaffold supports 700N. How much weight does the right end cable
support?
700N
Total force equals zero.
300N
300N + 400N + 400N – 700N - ? = 0
400N
400N
400N - ? = 0 , so the right cable must support 400N.
The object in each drawing weighs 400N. How much force supports the weight on each rope or lever? (The lever
moves 4 times farther than the object.)
A
400, B 400, C 200 (ignoring weight of pulley), D 200, E 100
E
A
B
400
C
400
D