This preview shows pages 1–3. Sign up to view the full content.
Student name________________________________________
Student NID__________________________________________
PHY 2053C_0001
Midterm exam 2, March 23, 2011, Chapters 47
1)
(
2 points
) A sled with people is sliding down the hill, as shown in Figure 1. The total weight of
the sled and people in it is
w
= 250 N, the slope angle is
α
= 35
o
, and there is no friction. Find the
acceleration of the sled and the normal force
F
N
.
mg
sin
α
=
ma
x
a
x
=
g
sin
α
= 5.6 m/s
2
F
N
=
mg
cos
α
=
w
cos
α
= 204.8 N
2)
(
2 points
) Two spheres, with masses
m
1
= 0.01 kg and
m
2
= 0.50 kg, are held at a distance
r
=
0.05 m. What would be the accelerations of each sphere at the moment when they are released,
a
1
and
a
2
, provided they only feel each other’s gravitational force (i.e., you can ignore all other
forces).
Hint:
3)
(
2 points
) A 0.02kg ball is shot from the plunger of a pinball machine. Because of a centripetal
force of 0.018 N, the ball follows a circular arc whose radius is 0.25 m. What is the speed of the
ball?
1
Figure 1
11
2
2
6.674 10
/
G
N m
kg

=
×
⋅
Figure 2
11
2
2
10
1
2
2
2
0.01
0.5
(6.674 10
/
)
1.33 10
0.0025
g
m m
kg
kg
F
G
N m
kg
N
r
m


×
=
=
×
⋅
=
×
10
8
2
1
1
10
10
2
2
2
1.33 10
1.33 10
/
0.01
1.33 10
2.66 10
/
0.50
g
g
F
N
a
m s
m
kg
F
N
a
m s
m
kg




×
=
=
=
×
×
=
=
=
×
2
c
c
v
F
m
r
F r
0.018N 0.25m
v
0.47m / s
m
0.02kg
=
×
=
=
=
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentStudent name________________________________________
Student NID__________________________________________
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '09
 Staff

Click to edit the document details