Page 46 - SP015 Past Years PSPM Chapter 1 -5 Ver.2020

PHYSICS PSPM SEM 1 1999 - 2017

PSPM JUN 2000/2002 SF015/2 No. 4

12.

load

spring

FIGURE 5.4

A 20 kg load is connected through a smooth pulley to a spring with constant force,
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k = 350 N m as shown in FIGURE 5.4. Initially the load is held so that it is at rest and
the spring is not extended. When the load is released, determine the velocity when the
elongation is 0.5 m. [4 m]

PSPM JUN 2000/2002 SF015/2 No. 12(b), (c)

13.
L
s

 30

FIGURE 5.5

FIGURE 5.5 shows a lorry of mass 2000 kg slides down a slope of angle  and

distance L. After going down the slope, the lorry passes through a flat road and then
climbs a second slope of angle 30.
(a) By neglecting friction,

(i) show that the instantaneous velocity of the lorry when passing through the
flat road is given by

2
v  2 gL sin  v

o
(Assume that the initial velocity of the lorry is v o.) [3 m]

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(ii) calculate the distance s on the second slope if given  = 25, v o = 25 m s
and L = 15 m. [4 m]

(b) If after going down the first slope, the lorry driver steps on the brake and stops at a
distance of 12 m on the flat road, what is

(i) the work done by the brake? [4 m]
(ii) the average force exerted by the brake? [3 m]

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