Download PEg KE and Spring Problems

Physics 513
Energy Problems
Name:
Date:
Gravitational Potential Energy:
1.) What is needed to have gravitational potential energy?
2.) What are the derived units of energy?
fundamental units?
What are the
3.) What is the gravitational potential energy of a 5 kg block
that is 120 m above the ground?
4.) An
energy
raised
by the
object raised a given distance acquires a potential
of 9.8 Joules. A second block with twice the mass is
the same distance. What is the potential energy acquired
second block?
5.) A book resting on shelf 10 m above the floor has a
gravitational potential energy of 980 J.
a)
What is the mass of the book?
b)
What is the new gravitational potential energy of the book
if it is moved down to a shelf 7 m above the floor?
Kinetic Energy:
1.) A baseball leaves a bat with a speed of 50 m/s. If the ball
weights 1.25 N, what is the kinetic energy of the ball?
2.) A 50 g arrow is fired from a bow. If a person did 150
Joules of work to pull back the bowstring:
a) What is the kinetic energy of the arrow?
b) What is the speed of the arrow when it leaves the bow?
3.) A 1000-kg car traveling at 20 m/s collides with a 1500 kg
truck that is at rest. The vehicles stick together and slide
forward at 8 m/s.
a) Did the collision follow the conservation of momentum
law?
b) What is the total kinetic energy of the vehicles before
the collision?
c) What is the total kinetic energy of the vehicles after
the collision?
d) Why does this not violate the law of conservation of
energy?
Roller Coasters
1. A roller coaster has three points of interest: A is at ground
level, B is 50 m above the ground at the top of the first hill,
and C is 30 m above the ground at the top of the second hill.
a) What is the minimum speed the cart must have at A to reach B?
b) If the cart has that minimum speed at A, how fast will it be
going when it reaches C?
2. A roller coaster cart starts at rest 80 m above the ground,
and plunges down a hill to ground level. There is a circular
loop, with its base on the ground, in the track. What is the
maximum radius of this loop such that the cart will make it
around without requiring safety equipment?
Springs
1. A mass of .75 kg is fired vertically by a compressed spring.
The spring is originally compressed by a net force of 75 N, and
has a k of 40 N/m. All of the energy from the spring is
transferred into the mass.
a) How far is the spring compressed?
b) How fast is the mass going when it leaves the spring?
c) How high, with respect to its starting position, does the
mass go?
2. A mass of 4 kg is attached to two springs, one on its right
and one on its left. Each spring starts at its natural length,
and they have spring constants of 125 N/m and 80 N/m. The mass
is pushed 60 cm to the right and then released.
a) How much force was required to move the mass 60 cm to its
right?
b) What is the maximum velocity the mass will achieve after its
release?
3. An object is dropped from 5 meters above a spring and lands
on the spring. If this causes the spring to compress .9 m and
the spring has a k of 900 N/m:
a) What is the mass of the object?
b) What is the maximum velocity of the object, and where does it
reach this velocity?
c) What is the maximum force between the mass and the spring?