1. A 250g ball attached to a string is rotating in a horizontal circle of radius 0.50 m.

1
Examples, Concept Questions and Problems
Chapter 5
1. A 250-g ball attached to a string is rotating
in a horizontal circle of radius 0.50 m.
If the ball revolves twice every second, what is
(a) balls speed?
(A) 2.3 m/s (B) 4.3 m/s (C) 6.3 m/s (D)
8.3 m/s (E) 10.3 m/s
(C)
(A) 2.0 N (B) 5.0 N (C) 7.0 N (D)
10.0 N (E) 20.0 N
(b) the tension in the string?
(E)
2. A plane is traveling at 200 m/s following the
arc of a vertical circle of radius R. At the top
of its path, the passengers experience
"weightlessness." To one significant figure,
what is the value of R?
(A) 200 m (B) 1000 m (C) 2000 m (D)
4000 m (E) 40000 m
(D)
2
Chapter 5
Examples, Concept Questions and Problems
3. A 1000-kg car travels along a straight 500-m
portion of highway (from A to B) at a constant
speed of 10 m/s. At B, the car encounters an
unbanked curve of radius 50 m. The car follows
the road from B to C traveling at a constant
speed of 10 m/s while the direction of the car
changes from east to south.
(a) What is the magnitude of the acceleration of
the car as it travels from A to B?
(A) 8 m/s2 (B) 6 m/s2 (C) 4 m/s2 (D) 2
m/s2 (E) 0 m/s2
(E)
(b) What is the magnitude of the acceleration of
the car as it travels from B to C?
(A) 8 m/s2 (B) 6 m/s2 (C) 4 m/s2 (D) 2
m/s2 (E) 0 m/s2
(D)
(c) What is the magnitude of the frictional force
between the tires and the road as the car
negotiates the curve from B to C?
(A) 20000 N (B) 10000 N (C) 5000 N
(D) 2000 N (E) 1000 N
(D)
3
Examples, Concept Questions and Problems
Chapter 5
Problem 5-18 (8)
(a) T ?
(b) v ?
4
Chapter 6
Examples, Concept Questions and Problems
1. The Force of Gravity (Dropping a basketball)
Fig. 6.10
v0 0 vf ?
W ?KE KEf - KE0
If v0 is not zero?
h hf h0
Fig. 6.11
Fig. 6.18
5
Chapter 6
Examples, Concept Questions and Problems
Example 4. The amount on energy needed to power a
100-W bulb for one minute would be just
sufficient to lift a 1.00-kg object through a
vertical distance of
(A) 0.2 m (B) 2 m (C) 12 m (D)
220 m (E) 610 m
(E)
6
Chapter 6
Examples, Concept Questions and Problems
Example 5.
W between 2 m and 8 m?
(1)
W 204 452 170 J
(2)
Fig. 6.23
7
Chapter 6
Examples, Concept Questions and Problems
6. PROBLEM 6-82.
m1 11 kg m2 44 kg

• VB ?
• KEB ?

7.67 m/s
323 J
1.29 kJ
?KE ?PE 0
4.43 m/s
8
Chapter 6
Examples, Concept Questions and Problems
8. 9.0-kg box of oranges slides from rest down a
frictionless incline from a height of 5.0 m. A
constant frictional force, introduced at point A,
brings the box to rest at point B, 19 m to the
right of point A.
(a) What is the speed of the block just before it
reaches point A?
(A) 98 m/s (B) 21 m/s (C) 9.9 m/s (D) 5.7
m/s (E) 4.4 m/s
?KE ?PE 0
(C)
(b) What is the coefficient of kinetic friction
µk of the surface from A to B?
(A) 0.11 (B) 0.26 (C) 0.33 (D) 0.47 (E) 0.52
?KE ?PE Wnc
or
(B)
9
Chapter 6
Examples, Concept Questions and Problems
In general
W ?KE
Example 9
10
10. Downhill Skateboarding
Chapter 6
Examples, Concept Questions and Problems
Fig. 6.24
v0 0 vf ?
o
W W1 W2 W3
11
Chapter 6
Examples, Concept Questions and Problems
11. A 10.0-kg crate slides along a horizontal
frictionless surface at a constant speed of 4.0
m/s. The crate then slides down a frictionless
incline and across a second horizontal surface.
(a) What is the kinetic energy of the crate as it
slides on the upper surface?
(A) 30 J (B) 80 J (C) 140 J (D) 290 J
(E) 490 J
(B)
(A) 30 J (B) 80 J (C) 140 J (D) 290 J
(E) 490 J
(b) While the crate slides along the upper
surface, how much gravitational potential energy
does it have compared to what it would have on
the lower surface?
(D)

• 290 J
• (B) 320 J
• (C) 370 J
• (D) 490 J
• (E) 570 J

(c) What is the kinetic energy of the crate as it
slides on the lower surface?
(C)
(d) What minimum coefficient of kinetic friction
is required to bring the crate to a stop over a
distance of AB 5.0 m along the lower surface?
(A) 0.30 (B) 0.32 (C) 0.60 (D) 0.66 (E)
0.76
(E)
12
Chapter 6
Examples, Concept Questions and Problems
12. The kinetic energy of a car is 8?106 J as it
travels along a horizontal road. How much work
is required to stop the car in 10 s?

• 0 J
• 8?104 J
• 8?105 J
• (D) 8?106 J
• (E) 8?107 J

(D)
W KE0
13. A 10.0-g bullet traveling horizontally at 755
m/s strikes a stationary target and stops after
penetrating 14.5 cm into the target. What is
the average force of the target on the bullet?
(A) 1.97?104 N (B) 2.07?105 N (C) 6.26?103
N (D) 3.13?104 N (E) 3.93?104 N
(A)
14. A dam is used to block the passage of a river
and to generate electricity. Approximately
5.73?104 kg of water fall each second through a
height of 19.6 m. If one half of the
gravitational potential energy of the water were
converted to electrical energy, how much power
would be generated?

• 1.25?105 N
• 5.50?106 N
• 3.80?107 N
• (D) 5.50?108 N
• 4.80?109 N

(B)
P mgh
13
Chapter 6
Examples, Concept Questions and Problems
15. Two boxes are connected to each other. The
system is released from rest and the 1.00-kg box
falls through a distance of 1.00 m. The surface
of the table is frictionless. What is the
kinetic energy of box B just before it reaches
the floor?
(A) 9.80 J (B) 4.90 J (C) 2.45 J (D) 1.22
J (E) 0.61 J
(C)
14
Examples, Concept Questions and Problems
Chapter 6
16. A crate of mass 10.0 kg is pulled up a rough
incline with an initial speed of 1.44 m/s. The
pulling force is 106 N parallel to the incline,
which makes an angle of 20.0 with the
horizontal. The coefficient of kinetic friction
is 0.400, and the crate is pulled 4.95 m. (a)
How much work is done by gravity?
(A) 66 J (B) 66 J (C) 166 J (D)
166 J (E) 266 J
(C)
(b) How much energy is lost because of friction?
(A) 142 J (B) 142 J (C) 182 J (D)
182 J (E) 222 J
(D)
(c) How much work is done by the 106 N force?
WT 524.7 J 525 J
(d) What is the change in kinetic energy of the
crate?
(A) 176 J (B) 176 J (C) 691 J (D)
509 J (E) 509 J
W ?KE
W Wg Wf WT
(A)
(e) What is the speed of the crate after it has
been pulled 4.95 m?
6.11 m/s