Transcript File - Mr. Graham`s AP Physics 1 & AP Physics C

AP Physics Review Ch 4 – Forces and Newton’s Laws of Motion
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Be able to apply Newton’s three laws to conceptual questions
Be able to draw free body diagrams and determine the magnitude of each force;
from your free body diagram, write an equations for both the x and y axes; if the
object is in equilibrium, then F=0; if the object is accelerating, then F=ma
Be able to calculate the normal force (not necessarily equal to mg)
Be able to solve force problems involving friction (fN)
Be able to solve tension problems including objects hanging from cables at various
angles and frictionless pulley problems
Be able to calculate the force of gravity and the acceleration due to gravity on
different planets
Know the definition of inertia and how it is measured
Be able to identify action-reaction pairs and know that they are always equal
Useful equations to know:
A Martian lander is approaching the
surface. It is slowing its descent by
firing its rocket motor. Which is the
correct free-body diagram for the
lander?
A Martian lander is approaching the
surface. It is slowing its descent by
firing its rocket motor. Which is the
correct free-body diagram for the
lander?
A satellite orbits the earth with constant speed at height
above the surface equal to the earth’s radius. The
magnitude of the satellite’s acceleration is
A. gon earth.
B. gon earth.
C. gon earth.
D. 2gon earth.
E. 4gon earth.
A satellite orbits the earth with constant speed at height
above the surface equal to the earth’s radius. The
magnitude of the satellite’s acceleration is
A. gon earth.
B. gon earth.
C. gon earth.
D. 2gon earth.
E. 4gon earth.
The figure shows a binary star system.
The mass of star 2 is twice the mass of
star 1. Compared to
, the magnitude
of the force
is
A. one quarter as big.
B. half as big.
C. twice as big.
D. four times as big.
E. the same size.
The figure shows a binary star system.
The mass of star 2 is twice the mass of
star 1. Compared to
, the magnitude
of the force
is
A. one quarter as big.
B. half as big.
C. twice as big.
D. four times as big.
E. the same size.
A planet has 4 times the mass of the earth, but the
acceleration due to gravity on the planet’s surface is the
same as on the earth’s surface. The planet’s radius is
A.
Re.
B.
Re.
C. Re.
D. 2Re.
E. 4Re.
A planet has 4 times the mass of the earth, but the
acceleration due to gravity on the planet’s surface is the
same as on the earth’s surface. The planet’s radius is
A.
Re.
B.
Re.
C. Re.
D. 2Re.
E. 4Re.
An elevator that has descended from the 50th floor
is coming to a halt at the 1st floor. As it does, your
apparent weight is
A.
B.
C.
D.
More than your true weight.
Less than your true weight.
Equal to your true weight.
Zero.
An elevator that has descended from the 50th floor
is coming to a halt at the 1st floor. As it does, your
apparent weight is
A.
B.
C.
D.
More than your true weight.
Less than your true weight.
Equal to your true weight.
Zero.
A rock is attached to a string and hangs from the ceiling of an
elevator. As the elevator is moving downward and slowing to a
stop, the tension in the string is
A.
B.
C.
D.
greater than the weight of the rock.
less than the weight of the rock.
equal to the weight of the rock.
Zero.
A rock is attached to a string and hangs from the ceiling of an
elevator. As the elevator is moving downward and slowing to a
stop, the tension in the string is
A.
B.
C.
D.
greater than the weight of the rock.
less than the weight of the rock.
equal to the weight of the rock.
Zero.
All three 50 kg blocks are at rest. Is the tension in rope 2
greater than, less than or equal to the tension in rope 1?
A. greater than
B. less than
C. equal to
All three 50 kg blocks are at rest. Is the tension in rope 2
greater than, less than or equal to the tension in rope 1?
A. greater than
B. less than
C. equal to
In the figure to the
right is the tension in
the string greater than,
less than, or equal to
the weight of block B?
A. Greater than
B. Less than
C. Equal to
In the figure to the
right is the tension in
the string greater than,
less than, or equal to
the weight of block B?
A. Greater than
B. Less than
C. Equal to
A small car is pushing a
larger truck that has a
dead battery. The mass
of the truck is larger than
the mass of the car. Which of the following statements is true?
A. The car exerts a force on the truck but the truck doesn’t
exert a force on the car.
B. The car exerts a larger force on the truck than the truck
exerts on the car.
C. The car exerts the same amount of force on the truck as
the truck exerts on the car.
D. The truck exerts a larger force on the car than the car
exerts on the truck.
E. The truck exerts a force on the car but the car doesn’t
exert a force on the truck.
A small car is pushing a
larger truck that has a
dead battery. The mass
of the truck is larger than
the mass of the car. Which of the following statements is true?
A. The car exerts a force on the truck but the truck doesn’t
exert a force on the car.
B. The car exerts a larger force on the truck than the truck
exerts on the car.
C. The car exerts the same amount of force on the
truck as the truck exerts on the car.
D. The truck exerts a larger force on the car than the car
exerts on the truck.
E. The truck exerts a force on the car but the car doesn’t
exert a force on the truck.
Is the tension in rope 2 greater than, less than, or equal
to the tension in rope 1?
A. greater than rope 2
B. less than than rope 2
C. equal to rope 2
Is the tension in rope 2 greater than, less than, or equal
to the tension in rope 1?
A. greater than rope 2
B. less than than rope 2
C. equal to rope 2
A
Consider two identical blocks, one
resting on a flat surface, and the
other resting on an incline. For
which case is the normal force
greater?
(A) case A
(B) case B
(C) both the same (N = mg)
(D) both the same (0 < N < mg)
(E) both the same (N = 0)
B
Three blocks of mass 3m, 2m, and m are connected by
strings and pulled with constant acceleration a. What is the
relationship between the tension in each of the strings?
a
(A) T1 > T2 > T3
T2
T3
T1
3m
(B) T1 < T2 < T3
2m
m
(C) T1 = T2 = T3
(D) all tensions are zero
(E) tensions are random
Below you see two cases: a physics
student pulling or pushing a sled
with a force F which is applied at
an angle q. In which case is the
normal force greater?
Case 1
Case 2
(A) case 1
(B) case 2
(C) it’s the same for both
(D) depends on the magnitude of the force F
(E) depends on the ice surface
In the Atwood machine shown in the
diagram, if m1 = 0.40 kg and m2 = 0.60 kg,
what is the magnitude of the acceleration of
the system? (Ignore friction and the mass
of the pulley.)
m2
m1
(A) 5.3 m/s2
(B) 3.9 m/s2
(C) 0.98 m/s2
(D) 2.0 m/s2
 F  ma
What is the acceleration of the 4
kg mass if there is no friction
between the 2kg mass and the
horizontal surface?
(A) 0.0 m/s2
(B) 2.0 m/s2
(C) 4.0 m/s2
(D) 6.7 m/s2
(E) 10 m/s2
What is the acceleration of the 4
kg mass if there is no friction
between the 2kg mass and the
horizontal surface?
(A) 0.0 m/s2
(B) 2.0 m/s2
(C) 4.0 m/s2
(D) 6.7 m/s2
(E) 10 m/s2
A traffic light of weight 100 N is supported by two
ropes as shown in the diagram. What are the tensions
in the ropes?
37o
37o
(A) 50 N
(B) 63 N
(C) 66 N
(D) 83 N
F0