Question

**Questions (use complete sentences)**

1) What is a conservation law? What is the basic approach taken when using a conservation law?

2) Could the linear momentum of a turtle be greater than the linear momentum of a horse? Explain.

3) Carts A and B stick together whenever they collide. The mass of A is twice that of B. How could you roll the carts so that they would be stopped after a collision?

4) How can a satellite’s speed decrease without its angular momentum changing?

**Problems (show your work)**

1) What is the linear momentum of an object with mass 50 kg and speed 15 m/s?

2) A 0.25 kg ball of clay is thrown at a stationary 5 kg block of wood. The clay sticks to the wood and their velocity after is 3 m/s. What was the original velocity of the clay?

3) A 50 kg boy on skates moves with a speed of 5 m/s. He runs into a stationary girl with skates of mass 40 kg. Assuming they stick together, what is their speed after the collision?

4) A running back with a mass of 80 kg and speed 8 m/s collides with, and is held by, a 120 kg defensive tackle going in the opposite direction. How fast must the tackle be going before the collision for their speed afterward to be zero?

5) An object is pushed along a horizontal surface with a force of 10 N. If the object is moved 15 m, how much work does the pushing force do? How much work does gravity do?

6) As it orbits the Earth, the 11,000 kg Hubble Space Telescope travels at a speed of 7,900 m/s and is 560,000 m above the Earth’s surface. What is its kinetic and potential energy?

7) A child on a swing has a speed of 7.7 m/s at the low point of the arc. What will be the maximum height of the child?

8) If an object is thrown straight up and reaches a height of 20 m, what was the initial speed of the object?

9) An object of 2 kg is moving in a circle of radius 4 m and speed 0.5 m/s. What is the angular momentum of the object?

**Challenges (show work)**

1) A bullet of mass 0.01 kg is fired horizontally into a block of wood of mass 2 kg. The wood is hanging on a string initially at rest. When the bullet hits the wood it gets embedded into the wood then they swing upward to a height of 0.1 m. What was the initial speed of the bullet?

Answer #1

Revisiting the ballistic pendulum. In lab we used both
conservation of momentum and conservation of energy to relate the
launch speed of a projectile to the maximum height of the swing of
a pendulum. Here we will study the parts of this problem in a bit
more detail.
(a) Briefly explain why momentum is conserved during the
collision of the projectile and the pendulum, but mechanical energy
is not conserved.
(b) Briefly explain why mechanical energy (kinetic plus
potential energy)...

Question 1: A ball of clay (m= 20 g) is thrown horizontally at a
block of wood (m=1.0 kg) that is sitting at rest on a frictionless
surface. The ball of clay has a speed of 30 m/s. When it hits the
block, it sticks to it. a) (1 point) What type of collision is
this? b) (3 points) What is the speed of the block and the clay
right after the collision? c) (2 points) Calculate the impulse
(change...

A 0.00400-kg bullet traveling horizontally with speed 1.00 103
m/s strikes a 20.0-kg door, embedding itself 10.9 cm from the side
opposite the hinges as shown in the figure below. The 1.00-m wide
door is free to swing on its frictionless hinges. (a) Before it
hits the door, does the bullet have angular momentum relative the
door's axis of rotation? Yes No (b) If so, evaluate this angular
momentum. (If not, enter zero.) kg · m2/s If not, explain why...

A 0.00400-kg bullet traveling horizontally with speed 1.00 103
m/s strikes a 17.7-kg door, embedding itself 10.2 cm from the side
opposite the hinges as shown in the figure below. The 1.00-m wide
door is free to swing on its frictionless hinges. (a) Before it
hits the door, does the bullet have angular momentum relative the
door's axis of rotation? Yes No (b) If so, evaluate this angular
momentum. (If not, enter zero.) kg · m2/s If not, explain why...

A 0.00600 kg bullet traveling horizontally with speed 1.00
103 m/s strikes a 21.4 kg door, embedding itself 11.3 cm
from the side opposite the hinges as shown in the figure below. The
1.00 m wide door is free to swing on its frictionless hinges.
A door shown from above such that its hinge is on the top side
of the figure with the door going down. A bullet is traveling
horizontally to the right towards the door on the...

1. A loaded gun is dropped on a frozen lake. The gun fires, with
the bullet going horizontally in one direction and the gun sliding
on the ice in the other direction. The bullet's mass is 0.04 kg,
and its speed is 305 m/s. If the gun's mass is 1.8 kg, what is its
speed (in m/s)?
______m/s
2. A 37 kg child uses a pogo stick to bounce up and down. The
spring constant, k, of the toy equals...

1. You shoot a bullet of mass m=0.025 kg into a wood box of mass
M=1.7 kg which initially is at rest. After the impact, the wood
with embedded bullet moves to the flat top of the hill, and it
continues its motion on the top. Initial speed of the bullet before
collision is vo=560 m/s. The height of the hill is h=0.3 m. The
surface has no friction. At what speed the wooden block moves on
the top of...

A 0.005 kg bullet traveling horizontally with speed 1.00 x
103 m/s strikes an 18.0-kg door, embedding itself 10.0
cm from the side opposite the hinges. The 1.00 m wide door is free
to swing on its frictionless hinges.
A) What is the bullet’s initial angular momentum relative to the
door’s axis of rotation?
B)At what angular speed does the door swing open immediately
after the collision?

A heavy 3.8 kg block moves at 4.2 m/s and then makes a head-on
elastic collision with a lighter, stationary block of mass 1.7 kg.
Use conservation of momentum and the fact that the relative speed
of recession equals the relative speed of approach to find velocity
of each block after the collision. Check your answer by calculating
the initial and final kinetic energies of each block.
Show work and explain

Part 1. A 1350-kilogram truck moving with a speed of 22.0 m/s
runs into the rear end of a 1290-kilogram stationary car. If the
collision is completely inelastic, how much kinetic energy is lost
in the collision?
Part 2. An 20 g rifle bullet traveling at 290 m/s buries itself
in a 5.4 kg pendulum hanging on a 3.2 m long string, which makes
the pendulum swing upward in an arc. Determine the maximum vertical
displacement of the pendulum (height).(g...

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