Transcript An 875 kg car speeds from 22 m/s to 44 m/s. What were its initial and

An 875 kg car speeds from
22 m/s to 44 m/s. What
were its initial and final
energies?
If you lift a 2 kg textbook
from the floor to a shelf 2.1
m above the floor. What is
PEg relative to the floor?
Relative to your
head if you are
1.65 m tall?
A slinky is stretched a
distance of 3 m. If the
amount of energy in the
spring is 310 J, what is the
spring constant?
What would be the
velocity of a 0.500 g
raindrop if it fell 0.250
km to the ground without
any resistance provided
by air?
A 100.0 g arrow is pulled
back 30.0 cm against a
bowstring. If the spring
constant of the bowstring
is 1250 N/m, at
what speed will
the arrow leave
the bow?
Suppose a squirrel sitting on
top of a redwood tree drops a
20 g walnut. If the speed of the
falling walnut at the moment
it is 50 m above the
ground is 42.7 m/s,
how tall is the
tree?
Suppose a coin is dropped
from a hot air balloon at a
height of 3150 m. How high
above the ground
is the coin when its
speed is 60.0 m/s?
Block whose mass is 5.7 kg slides on a
horizontal frictionless tabletop with a
constant velocity of 1.2 m/s. It is
momentarily brought to rest as it
compresses a spring in its path. By
what distance is the spring
compressed? The spring constant is
1500 N/m.
v=0
A 0.4 kg ball starts from rest
at point A and slides along a
frictionless curved wire. What
is the velocity at point B?
Point C?A
C
5m
2m
B
A 2000 kg roller coaster that has
a vertical drop of 68.6 m, is
designed so that the speed of the
cars at the end of
this drop is 35.6 m/s. Assume the
cars are at rest at the start of the
drop. What amount of the initial
mechanical energy is dissipated
by friction?
= 97 N
= 20 N
=5m
= 147 N
An applied force of 92 N is
exerted horizontally on an 18 kg
box of books. The coefficient of
kinetic friction is 0.35. If the box
is initially at rest,
what is net work done
after has been
moved 7.6 m?
A wagon is pulled rightward a
horizontal distance of 15.0 m.
The handle of the wagon makes
an angle of 20.0° with the
horizontal, and the girl exerts a
force of 35.0 N on the handle.
Friction provides a force of 24.0
N. Find the net work that is done
on the wagon.
A force of 102 N moves the
800 kg boat
0.90
km.
Assume
A 2.00 × 102 kg iceboat is
propelled across the horizontal
that frictional
forces
are
surface of a
frozen lake by the wind. The wind
negligible
that
exertsand
a constant
force of 4.00 ×
the boat starts
from rest.
What is the boat’s
final speed?
A hockey puck with an initial
speed of 8.0 m/s coasts 45 m to
a stop across the ice. If the
force of friction on the puck
has a magnitude of 0.12 N,
what is the
puck’s mass?
A crane hoist lifts a load of
1000 kg a vertical distance
of 25 m in 9.0 s, at a
constant velocity. What is
the power of the
Crane?
A runner exerts a force of 334
N against the ground and is
exerting 2100 W of power.
How long does it take
the runner to run
a distance of
50.0 m?
A railway car with a mass of 8500 kg
and a velocity of 4.5 m/s to the right
collides in-elastically with a railway car
with a mass of 9800 kg and a velocity
of 3.9 m/s to the left. What is the final
velocity of the combined cars? How
much KE was lost?
KE = ?
vf= ?
Before
Colliding Trains (in-elastic)
After
m1 = 18,000 kg
v1i = 8 m/s
m2 = 24,000 kg
v2i = 0 m/s
A 5 kg ball moves to the right at 20 m/s
and elastically collides with a 10 kg
ball that is initially at rest. After the
collision the 5 kg ball moves to the left
at 6.68 m/s. What is the velocity of the
10 kg ball after the collision? Check
your answer using conservation of KE.
A 10 kg ball moving to the right
elastically collides with a 15 kg ball
that is moving to the left at 30 m/s.
After the collision, the 10 kg ball
moves to the left at 40 m/s and the 15
kg ball moves to the right at 10 m/s.
What was the initial velocity of the 10
kg ball? Check your answer using
cons. of KE