Download free-body diagram (FBD) worksheet:

free-body diagram (FBD) worksheet:
Draw in “action-at-a distance” forces (Fgrav, Felec, Fnuke, etc) and, then, ALL other forces MUST be “contact” forces.
Newton’s 2nd Law tells us that the vector sum of all of the forces acting on a body equals its mass x acceleration. We can look at the FBD to see how
a body’s motion will change AND we can look at how a body’s motion is changing and make assumptions about the forces that must be acting on it.
Draw a FBD for a
block at rest on a
horizontal surface
Draw a FBD for a
block being pushed
on a horizontal,
frictionless surface
Label the
magnitude of the
forces for a 10-kg
block
Label the magnitude
of the forces and
find the acceleration
for a 10-kg block
with a push of 50N.
Draw a FBD for a
block being pushed on
a rough, horizontal
surface
Draw a FBD for a block
being pushed on a
horizontal surface at a
constant velocity.
Label the magnitude
of the forces and find
the acceleration for a
10-kg block with a
push of 50N & a 30N
friction force.
Find the acceleration &
label the magnitude of
the forces for a 10-kg
block with a push of
50N & a constant
velocity of 30m/s.
Draw a FBD for a
block sliding to a stop.
Draw a FBD for a block on a
frictionless incline.
Label the magnitude
of the forces for a 5 kg
block that is initially
traveling at 30 m/s and
slows to a stop in 5 s.
Find the acceleration of a
10-kg block on a 30o incline.
Written by John Burgholzer, Amherst Central HS, 2010
Draw a FBD for a block at
rest on an incline.
Draw a FBD for a block
accelerating down a rough
incline.
Find the friction force for a
10-kg block on a 30o incline.
Find the friction force acting on a
10-kg block on a 30o incline that
accelerates at 2 m/s2
The floor is frictionless. The
top block moves with the
bottom block. Draw a FBD
for the two blocks together
& for the individual blocks.
The big block is 10 kg. Find
the magnitude of all of the
forces present if the applied
force = 36N and the system
accelerates at 3 m/s2
Ignoring air resistance, draw a FBD…
…for an object dropped from rest.
…for an object thrown straight upwards.
…for an object thrown at an angle to the horizontal.
Ponder these…
What is the definition of freefall?
How can such different motions
result from these FBDs?
IF we chose to think about air
resistance, in which direction
would Fair be in each of these?
Draw FBDs for these situations.
How do we find Fnet?


a
If the mass is 5 kg and a = 2 m/s2,
what angle does the string make
with the vertical?
Draw a FBD for a person in an elevator when the elevator is…
…moving at
constant speed.
…accelerating
upwards.
…accelerating
downwards.
His mass is 80 kg. What does the scale read when the speed in the
1st diagram is 5 m/s and the acceleration in the other two is 2 m/s2?
Which way is the elevator moving in each case?
Draw a FBD for the 500-kg jet. If the thrust
is 10,000 N and the plane accelerates
horizontally at 8m/s2, what is the drag force?
Draw a FBD for the
100-kg rocket. If the
thrust is 10,000 N,
what is the
acceleration of the
rocket?
Fair = zero
Al, a BASE jumper, leaps off a cliff. He weighs 1000N so his
mass = _______kg. The resistive force due to the air (Fair)
varies with his speed and the surface area presented to the air.
Using Newton’s 2nd Law, Al’s acceleration (a) is…
a = _________
weight = 1000 N
1
a = Fnet = weight - Fair
m
mass
Given the values for weight and Fair for each segment of his trip,
calculate his acceleration at each point.
Fair = 600 N
a = _________
(Note: The answers below are important, but knowing
WHY they are correct is much more important!)
weight = 1000 N
2
Circle the correct answers:
1. When Al’s speed is least, his acceleration is…
[least] [most] [the same].
Fair = 1000 N
2.
In which position(s) does Al experience a downward acceleration?
[1]
[2]
[3]
[4]
[5]
3.
In which position(s) does Al experience an upward acceleration?
[1]
[2]
[3]
[4]
[5]
4.
When Al’s acceleration is upward, his velocity is…
[directed upwards]
[directed downwards]
AND his speed is…
[decreasing]
[increasing]
[constant].
5.
In which position(s) is Al’s velocity constant?
[1]
[2]
[3]
[4]
[5]
6.
In which position(s) does Al’s experience terminal velocity?
[1]
[2]
[3]
[4]
[5]
7.
In which position(s) is Al moving at the greatest speed?
[1]
[2]
[3]
[4]
[5]
8.
If Al were heavier, his fastest (terminal) speed would be…
[greater]
[less]
[the same].
a = _________
weight = 1000 N
3
Fair = 1600 N
a = _________
weight = 1000 N
4
Fair = 1000 N
a = _________
weight = 1000 N
5