Maria sets up a simple track for her toy block (m = 0.25 kg) as shown in Figure

Question

Maria sets up a simple track for her toy block (m = 0.25 kg) as shown in Figure P9.77. She holds the block at the top of the track, 0.54 m above the bottom, and releases it from rest, a. Neglecting friction, what is the speed of the block when it reaches the bottom of the curve (the beginning of the horizontal section of track)? b. If friction is present on the horizontal section of track and the block comes to a stop after traveling 0.75 m along the bottom, what is the magnitude of the friction force acting on the block?

Explanation / Answer

using the conservation of energy,

PE at top of track = kE at the bottome of track

mgh = 0.5 mv^2

(9.8) (0.54) = 0.5 v^2

v = 3.253 m/s apprx

b) using the work energy theorem

Initial KE = work done to overcome friction

0.5 ( 0.25) ( 10.584) = F ( 0.75)

Frictional forc e= 1.764 N apprx

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