**3]** The concept of "impulse" is often
used when dealing with the impact forces involved in

collisions. Two darts are
thrown with the same speed at a standing block of wood. Although

they are identical in mass,
one dart has a pointed tip (it sticks in the wood) while the other

has a rubber tip (it bounces
back from the wood). Explain which dart will be more successful

in providing the force
necessary
to knock over the block of wood using the concept of

impulse to justify your
reasoning.

What was the impulse imparted to Ball 2 ?

Answer: 40 N x sec
(opposite
initial vel. direction) *[will **need to find** final vel. of ball
2
= 2.7 m/s]

3] A) A 10.0 kg object that is
moving
to the right with a constant velocity collides head-on with

a 15.0 kg object that is
initially at rest. The two objects stick together and move off to the
right

with a velocity of 8.00
cm/s. What was the initial velocity (don’t forget direction!) of the

10.0 kg object?

Answer: 20.0 cm/s to the right

B) Now the
stuck
together masses moving to the right as one object have an elastic
head-on

collision with a 25.0 kg
mass that is at rest. Give the final velocities of both objects (the
stuck

together masses and the
25 kg mass) after the collision.

applies a force very much larger than the weight of the ball and the ball departs from the bat

with a final velocity of 58 m/s in a direction

time between the bat and the ball is 4.0 x 10

by the bat?

Answer: 3360 N

1] A 0.150 kg object tied to a string is
whirled
in a horizontal circle at a constant angular speed

of 3.50 revolutions/sec.
The tension in the string is 75.0 N. What is the length of the string?

ANSWER: 1.03 m

2] A wheel of diameter 0.80 m is initially
at
rest. It is then rotated with a constant angular

acceleration of 5.0 rad/s^{2}
for exactly 10 revolutions of the wheel. Determine both the angular

speed of the wheel and the
tangential speed for a point on the edge of the wheel at the end

of the 10 revolutions.

ANSWER: 25 rad/s , 10 m/s

1] A 150 gm object tied to a string is
whirled
in a horizontal circle such that the tension in the

string is 75.0 N when the
angular speed is 3.50 revolutions/sec. How many meters, **s**, does

the object travel in 5.00
seconds? [ NOTE
**s** is the circumferential distance traveled around

the circle.]

3] A
uniform beam 3.00 meters long has a weight
of 245 N. It is supported on its left end by a cable.

A 500 N weight is located
on the beam a distance of 1.00 meter from the left end. You supply a

force to the right end of
the beam so that the beam is in equilibrium in the horizontal position
(see

sketch). What are the
tension
in the cable, T, and the upward force, F, you must apply to the beam?

** {HINT : Apply the
equilibrium
condition for two different axis’ of rotation !!}
**

I'll Add More Multiple Choice and
the Answers over the Weekend

5) It is correct to say that impulse is equal to

A) momentum

B) the change in momentum

C) the force multiplied by the distance the force acts

D) all the above (A, B, and C)

E) none of the above (A, B, or C)

6) A bullet is fired from a gun. The speed of the bullet will be about the same as the speed of the recoiling gun

A) as long as momentum is conserved.

B) because velocity will be conserved.

C) because both velocity and momentum are conserved.

D) only if the mass of the bullet is about the same as the mass of the gun.

E) none of the above are correct

7) Compared with falling on a wooden floor, a wine glass may not break when it falls on a carpeted floor because

A) the impulse imparted to it will be smaller.

B) the time during which the stopping force is applied will be longer.

C) both A) and B) are true.

D) neither A) nor B) are true.

8) Which one of the following statements is NOT true for a rotating CD undergoing angular acceleration?

A) The angular speed is the same at any point on the disk

B) The linear speed is the same at any point on the disk

C) The angular accerlation is perpendicular to the centripetal
acceleration

D) It may have zero angular velocity

E) The angular accerlation is the same for any point on the disk

a. only by a centripetal force.

b. only by a force directed radially outwards.

c. only by a tangential force.

d. only by a force with a component directed radially outwards.

e. by any force perpendicular to but not pointing directly toward or
away from the axis of rotation

10) Five
identical cylinders are each acted on by forces of equal magnitude.

Which force
exerts the biggest torque with respect to an origin located at the
center of
the cylinder?

ANSWERS:

5) B

6) D

7) B

8) B

9) E

10) A