HW Chapter 4
4.11 A hockey puck with mass 0.160 kg is at rest at the origin (x = 0) on the horizontal,
frictionless surface of the ring. At time t = 0 a player applies a force of 0.250 N to the
puck, parallel to the xaxis; he continues to apply this force until t = 2.00 s. a) What are
the position and speed of the puck at t = 2.00 s? b) If the same force is again applied at t =
5.00 s, what are the position and speed of the puck at t = 7.00 s?
4. 14 An electron (mass = 9.11
×
10
31
kg) leaves one end of a TV picture tube with zero
initial speed and travels in a straight line to the accelerating grid, which is 1.80 cm away.
It reaches the grid with a speed of 3.00
×
10
6
m/s. If the accelerating force is constant,
compute a) the acceleration; b) the time to reach the grid; c) the net force, in newtons.
(You can ignore the gravitational force on the electron.)
4.17 At the surface of Jupiter’s moon Io, the acceleration due to gravity is g = 1.81 m/s
2
.
A watermelon weighs 44.0 N at the surface of the earth. a) What is its mass on the earth’s
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 Spring '07
 D.V
 Force, Friction, Mass, frictionless horizontal surface, horizontal forces F1, 0.160 kg

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