Projected rotational velocities (
) and effective temperatures have
been derived for 
Sct stars as well as for 41 non-variable stars
in order to relate the physical parameters of a star with its pulsation
parameters. Rotational velocities were calculated using the method developed in
Gray (1992) which works well for spectra with moderate
resolution and good signal-to-noise.
Effective temperatures were determined by comparing observed
profiles with the theoretical profiles of Kurucz
(1979a). Extensive comparison was then made between these temperatures
and those derived using other methods (Infrared Flux Method,
spectrophotometric methods and 
photometric calibrations). A
systematic difference of 100 K between the effective temperatures
obtained using the 
line and the IRFM (Blackwell &
Lynas-Gray 1994) was found. No significant differences were
found between the effective temperatures derived from 
and from
spectrophotometric methods (Malagnini et al. 1986). The level of
agreement with temperatures from 
photometry depend on the
calibration used, the best agreement being with the Moon & Dworetsky
calibration (1985).
In the second part of this paper we relate 
and 
with the amplitude and period of the stars. There is a clear relation
between amplitude and 
with all the large amplitude pulsators having
low rotation velocities. Where modes are known, the large
amplitude stars are singe or double-mode radial pulsators whereas the low
amplitude stars are multimode pulsators with both radial and non-radial
modes excited. The multimode behaviour among low amplitude stars is
consistent with the suggestion by Dziembowski (1980) that
non-linear coupling between radial and non-radial modes limits the amplitudes.
Several stars seem to be anomalous: V1162 Ori is a radial large amplitude
pulsator with 
=46 
whereas GN And is a
single-mode low amplitude pulsator. In both cases, more extensive observing runs
could indicate the presence of new frequencies. Moreover CC And, a multimode
large amplitude star (
), may indicate an intermediate stage
where multimode pulsation and relatively large amplitude can coexist.
Comparing the distribution in 
of low amplitude 
Scutis and non-variable stars of the same spectral type, this shows a broader
distribution for the 
Scutis, suggesting that high rotation may
excite pulsation.
Comparing the period-temperature relations for the large and low
amplitude stars suggests that the large amplitude stars are preferentially
cooler and have longer periods. From their values of 
, 
,
period and their relative scarcity, the explanation proposed by Breger
(1980) that the large amplitude 
Sct stars are more evolved
(sub-giants) than the low amplitude 
Scutis (main sequence or
early post-main sequence) is consistent with observation.
Acknowledgements
We would like to thank Rafael Garrido for helpful comments. The authors would also like to acknowledge the constructive comments of an anonymous referee. This work has made use of the Simbad database, operated at CDS, Strasbourg, France.