KINEMATICS PROBLEMS
#2
YOUR NAME:
1.
Can an object move if there is no net force on it? Explain.
2.
Suppose you apply a force of 1
N to block A and a force of 2
N to block B.
Does it follow that block B has twice the acceleration of block A? Justif
y your
answer using Newton's second law.
3. When a brick rests on a flat, stationary, horizontal table,
there is an upward
normal
force on it from the table. Explain why the brick does not accelerate
upward in response to this force.
4.
A rock
et in space can change course with its engines. Since in empty space
there is nothing for the exhaust gases to push on, how can it accelerate?
5.
An airplane of mass 2867
kg flies at a constant horizontal velocity. The force
of air resistance on it is 2225
N. What is the net force on the plane
(magnitude and direction)?
6.
Three children are pulling on a toy that has a mass of 1.25
kg. Child A pulls
with force (5.00,
6.00,
2.50)
N. Child B pulls with force
(0.00,
9.20,
2.40)
N. With what force must Child C
pull for the toy to
remain stationary?
7.
(a) How much does a 70.0
kg person weigh on the Earth? (b) How much
would she weigh on the Moon (
g
moon
=
0.166
g
)? (c) How much would she
weigh on a neutron star where
g
star
=
1.43×10
11
g
?
8.
A dog on Earth weighs 1
36
N. The same dog weighs 154
N on Neptune. What
is the acceleration due to gravity on Neptune?
9.
When empty, a particular helicopter of mass 3770
kg can accelerate straight
upward at a maximum acceleration of
1.34
m/s
2
. A careless crewman
overloads the h
elicopter so that it is just unable to lift off. What is the mass of
the cargo?
10.
A 0.125
kg frozen hamburger patty has two forces acting on it that determine
its horizontal motion. A 2.30
N force pushes it to the left, and a 0.800
N
force pushes it to th
e right. (a) Taking right to be positive, what is the net
force acting on it? (b) What is its acceleration?
11.
A flea has a mass of 4.9×10
−7
kg. When a flea jumps, its rear legs act like
catapults, accelerating it at 2400
m/s
2
. What force do the flea's legs have to
exert on the ground for a flea to accelerate at this rate?
12.
An extreme amusement park ride accelerates its riders upward from r
est to
50.0
m/s in 7.00 seconds. Ignoring air resistance, what average upward force
does the seat exert on a rider who weighs 1120
N?
13.
A giant excavator (used in road construction) can apply a maximum vertical
force of 2.25×10
5
N. If it can vertically acc
elerate a load of dirt at 0.200
m/s
2
,
what is the mass of that load? Ignore the mass of the excavator itself.
14.
A tennis player strikes a tennis ball of mass 56.7
g when it is at the top of the
toss, accelerating it to 68.0
m/s in a distance of 0.0250
m. What is the
average
force the player exerts on the ball? Ignore any other forces acting on
the ball.
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