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HW4
52
2.
•
In a grocery store, you push a 12.5kg shopping cart with a force of
F= 14.0 N
.
If the cart starts at rest, how far does it move in 3.00 s?
sol 5
2.
2
ˆ
(14.0 N)
m
ˆ
1.12
12.5 kg
s
m
⎛⎞
==
=
⎜⎟
⎝⎠
Fx
ax
G
G
22
2
11
m
1.12
(3.00 s)
5.04 m
s
xa
t
Δ= Δ =
=
510
10.
••
A 747 jetliner lands and begins to slow to a stop as it moves along the
runway. If its mass is 350 10
5
.,
×
kg its speed is 27.0 m/s, and the net braking
force
is F=430 10
5
×
N
(a)
what is its speed 7.50 s later?
(b)
How far has it traveled in this time?
Sol 5
10. (a)
Determine the acceleration.
5
52
– 4.30 10 N
m
1.23
3.50 10 kg
s
F
a
m
×
=
−
×
Find the speed.
0
2
mm
27.0
1.23
(7.50 s)
17.8 m s
s
s
vv a
t
=+=
+
−
=
(b)
()
( )
2
2
2
ss
0
m
s
17.8
27.0
168 m
2
21
.
2
3
vv
x
a
−
−
Δ=
=
=
−
514
14.
••
On vacation, your 1300kg car pulls a 540kg trailer away from a stop light
with an acceleration of a=190
2
..
m/s
(a)
What is the net force exerted by the car on the
trailer?
(b)
What force does the trailer exert on the car?
(c)
What is the net force acting on
the car?
Sol 514.
m
= mass of the trailer
M
= mass of the car
(a)
The trailer is accelerating at 1.90 m/s
2
, so
net
2
m
(540 kg) 1.90
1.0 kN
s
Fm
a
=
(b)
The car exerts a force of 1.0 kN on the trailer. The trailer exerts an equal and opposite force on
the car. The trailer exerts a net force of 1.0 kN on the car.
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This note was uploaded on 07/02/2011 for the course PHYS 201 taught by Professor Woodahl during the Fall '09 term at Indiana.
 Fall '09
 WOODAHL
 Physics, Force, Work

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