We define experiments that measure user perception when video resolution changes dynamically. Versatile Video Coding (VVC) standard was recently finalized and it includes a reference picture resampling (RPR) tool. VVC RPR supports changing spatial resolution in a coded video sequence on a per picture basis. VVC RPR defines the downsampling and upsampling filters to be used when changing resolution. This paper provides results from subjective evaluation when VVC RPR is used for part of the video sequence to dynamically change resolution. The experiments use different QP values (or bitrates), different RPR scale factors and different highest original spatial resolutions. The results compare how users perceive video coded using VVC RPR for some pictures compared to an anchor which does not use RPR. In addition to the subjective results, we also describe performance of various metrics including PSNR, VMAF and MS-SSIM. Our results can help choose the highest RPR scale factor that can be used to achieve/ maintain certain perceived quality when using RPR (for example for bitrate reduction). The study also confirms that MS-SSIM and VMAF match subjective test results more closely compared to PSNR.