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Unformatted text preview: &\ “I”. 03 l. PHVS 230'. Mid—l“ch
W A book, initially at rest, is pushed along a horizontal table top by a horizontal force of 2N. After ls, it
has been moved 1.5 meters. The force of friction is 0.4N. (a) How much work is done on the book by the 2N force? (b) How much work is done on the book by friction? (c) What is the book’s kinetic energy after one second? in F ;o.L{I\/, (Hz: (S I tentr \MW: [Fix 2 F gold :QM)USml OJ. 2. A small block of mass m starts from rest and slides along (g m
a frictionless loop—theloop as shown in the ﬁgure on the right. When the mass m arrives at the top of the loop "\\ x
(marked by a) it just lost touch with the track. What \ {If ff}. ‘}
should be the initial height 2 7 \\ ‘2 . CL (Lt/Jar WLQJ“c “ K\*U\ .: KL%U1
mgh —— lamvl’rmétum 3. A prisoner with mass 70kg escapes from a cell window by sliding down a rope attached at the top end
to a hook which can support a pull of 6OON. The window is 45m above ground and the rope is long
enough to reach the ground. Assume the rope to be massless. What is the minimum speed the prisoner
can land on the ground? (Hint: obviously, if the prisoner does not slide down with enough acceleration, the hook will break and he will fall to injury). The “Ago. “ix Ari/ted: +\A—L Prisoner \r\a5 +0 sii‘cie
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69 mt LU v : Ck 3f CM /— 4. A tennis ball with mass M=60 grams strikes a racket. The incoming speed of the ball is V5120
km/hour, as observed by spectators in the tennis match. To simplify the situation, let’s assume that the
ball bounces straight back elastically within a time intewal of 0.1 seconds. (a) If the racket was stationary, what is the force exerted on the racket by the tennis ball? (b) The tennis player swings the racket with speed V590 km/hour toward the incoming ball. What is
the momentum of the ball after it is bounced back? (hint: you may think this racket as a moving
wall) (c) For case (b), what is the force felt by the racket? M: 0.060 K5 Va :tzotzw/lr A’c=O‘S Va 3 3 s7) 4 3 m /S
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This note was uploaded on 08/17/2011 for the course PHYS 230 taught by Professor Harris during the Winter '07 term at McGill.
 Winter '07
 Harris

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