Work done by a constant force
(a)Steve exerts a steady force of magnitude 210 N on a stalled car as he pushes it a distance of 18 m. The
car also has a flat tire, so to make the car track straight Steve must push at an angle of 30° to the direction
of motion. How much work does Steve do?
=
W Fscosφ
=
(
)
°
210 N 18 m cos30
=
3274 J
(b) In a helpful mood, Steve pushes a second stalled car with a steady force
= (
)  (
)
F
160 N i
40 N j
.
The displacement of the car is
= (
) + (
)
s
14m i
11 m j
.How much work does Steve do in this case?
=
+
W Fxx Fyy
=
+
(
)
160 N14 m 40 N 11 m
=
1800 J
Work done by several forces
A farmer hitches her tractor to a sled loaded with firewood and pulls it a
distance of 20 m along level ground . The total weight of sled and load is 14,700 N. The tractor exerts a
constant 5000N force at an angle of
36.9°
above the horizontal. There is a 3500N friction force
opposing the sled's motion. Find the work done by each force acting on the sled and the total work done
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 Spring '11
 McDemus
 Physics, Force, Work, track straight Steve, steady force, Ibeam w=mg Fy=wf, constant 5000N force, 3500N friction force

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