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<h2>HL Paper 1</h2><div class="question">
<p>The intensity of a wave can be defined as the energy per unit area per unit time. What is the unit of intensity expressed in fundamental SI units?</p>
<p>A. kg m<sup>−2 </sup>s<sup>−1</sup></p>
<p>B. kg m<sup>2 </sup>s<sup>−3</sup></p>
<p>C. kg s<sup>−2</sup></p>
<p>D. kg s<sup>−3</sup></p>
</div>
<h2 style="margin-top: 1em">Markscheme</h2>
<div class="question">
<p>D</p>
</div>
<h2 style="margin-top: 1em">Examiners report</h2>
<div class="question">
<p>The unit analysis in this question proved tricky for many HL candidates, with option A being the most common (incorrect) answer. The high discrimination index suggests that this question was more problematic for weaker candidates.</p>
</div>
<br><hr><br><div class="question">
<p>A student is verifying the equation</p>
<p style="text-align:center;"><span style="background-color:#ffffff;"><span class="mjpage mjpage__block"><math xmlns="http://www.w3.org/1998/Math/MathML" display="block" alttext="x = \frac{{2\lambda Y}}{z}">
<mi>x</mi>
<mo>=</mo>
<mfrac>
<mrow>
<mn>2</mn>
<mi>λ</mi>
<mi>Y</mi>
</mrow>
<mi>z</mi>
</mfrac>
</math></span></span></p>
<p style="text-align:left;">The percentage uncertainties are:</p>
<p style="text-align:center;"> </p>
<p style="text-align:center;"><img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAcUAAACfCAYAAACIo8KhAAAgAElEQVR4Ae3dD3STZZ4v8G8CKjKhsl1mJSkMHOi0OIeyaDt4d+RoKJjKKMgpKzpo005ZBRcdr562TBmYWS8M6KS3XmdAZbjNUMowq2O6+IerjbZbvagLmyCXcpV0Kqdqm+DAMKXNVf41zz1v/jVJkzZJ35I//facnuZ98/z9PO+TX973fZIqhBAC/KEABShAAQpQAEoaUIACFKAABSjgEWBQ5JFAAQpQgAIU8AowKPJQoAAFKEABCngFGBR5KFCAAhSgAAW8AgyKPBQoQAEKUIACXgEGRR4KFKAABShAAa8AgyIPBQpQgAIUoIBXgEGRhwIFKEABClDAKzA+nIRCoQi3m/soQAEKUIACKSMQz3fThA2KUkFSYIynwJTRYkMpkEABzq8E4rPqMSEQ78kdL5+OicODnaQABShAgWgEGBSjUWIaClCAAhQYEwIMimNimNlJClCAAhSIRoBBMRolpqEABShAgTEhwKA4JoaZnaQABShAgWgEGBSjUWIaClCAAhQYEwIMimNimNlJClCAAhSIRoBBMRolpqEABShAgTEhwKA4JoaZnaQABShAgWgEGBSjUWIaClCAAhQYEwIMinIOs7MdLa/WoFSjcH9NnvQ1Q4pFG2BsbEW70yVnTSMoqxftLS+jZt1OWK/4ivkSjaXZUCiyUdr4pXenC872VrxaswHPWZ2+hPxLgZELXLGiJluaI+vQ6PAfhN5ywx2LI69S3hLCzaFoargCR+M6z2tDaSMc0WQJShNvvUGFcGMYAQbFYYCie9oF58l6lObkYvF9ldgbeLS3/gprVi5C7rItaHFciq64UUx1xfpb/HDxA6h895uha7nyMV764SLcV3kE/UOn5LMUGFMCUc8hmVUSVa/M3Uj64hgU5RgipwUvPVrtDoZqfS3MtvPuL1MX4iLslr2o0qqB1n/BQ5veRHeynDAG9Xs6ius7IEQH6ounBz3DDQpQQC6B8VAXv+R5bagvhlquYlmOvAIiwg8gjR1/hhf4Rtjq7hOSF9TVovl8/6As/V0mUa6GAPJFVfMZIcRlYTet9eTRm4Tdn6NPWAxaAcwWetMX/r2izybMBr1QS3W4f+cKvcEkLPaL3jRfCJN+tiffHz8SFpNB6N31Qaj1O8Rhd7qAOv3lQMw2WMRlEZBfqtduEvqANO46Z28WdS96+6mrE7bAbvZ/Kup06oD+DTSdj8ILjOn5ddkiDLOlY3mtMNkvhwCFHIvuZwP2RTy+fcVcFHaLSRj0c71zRZoDtcJsO+9L4PnbZxPNdVVC6zvOtVWirtkm+vypfHVqxXbTH0W1Vjq+ffMv+K9nDkkZzwubudY/96T0ar1BmCx24ZkuAXPQP+999cwW+oh9C8gX0IbZ238rXnTPO7XQ1X3qrcPTgX5bndBJaSO8Jvm7mcYP4p1jESNfvAWmsXGErp0RzVX57gkzMDlCk4amCTjI/ZNDyhMmKPZ3ClP5wAQPnJjqcpPocs8238QKnqz+tO4gFlBn4MSKOigahOUvzaLKHWzvE3W2b/yd5AT0U0T9YEzPr7iD4lDHt0TfL/ostQOBLuA4h3q9MHV530RGnFNzhb6uzRsYw82p2UKr/f6g4OiZ9xdFl2l9wBvXgLb66w6Yg/55H66egLxDzt3D4i/N1Z46g96oDrxRV1c1i5C3A1Efo6meMN45xsunIz7x/gY9p3sAzMZts/4OYf9BJVSYljvLXdNnbZ/jTAx1ujqasct4AtDWwtLXD+mSbJdpvfvSi+O9UzgdejlWWw2T+/LtQDqYj+DEV3BfurlsMWC2VP9sAyyXBToq8ge3WV2M+ssWGNwJtTBY+iA6KpCfOQ9FJfkADuHlQ53wVH0BHYfehhlq6Lbqoc3gIRXD8DJprAIRj+8rgKsdr2w0oBVqaKvNsPcLiP4uNFfrAMdOPPbrQ+iFC72tu/CY8QTU+j341D2n+tH36R7o1Sewd9N+HOkNmVS+udd/HG8c/A+EnUOuU2jaJS2euRsGy1/dl0j7u0wol66ROv4vTp2OYj1BxL5FmrsLkFmwBCVSHea3cajjgkfT1YlDLx8CcB+2rvkBMmI1HuPp+QqW5AeAMqccTUKgf//t6DIfQKNxMx5audOzcu3rczj/deAEVkNXoseKHGkaXIusfyjEnbL2LxMFRTqo4YD55Q/RIVXtPI7XG6QJuBD3L5wJHlCygrOwIIFhju+vPsF7ZmmV23I8/vgiqKWDUZmFwm1N7iBlf7YQGfgafzr6kXv+OPaW4aZJ46BQjMOkm8o8C+QcZjRZzgXUKtW5FDerlIByIlQTIxzhyjkob7JD9O/Goq4WNDbuRvVDj8HoXnTXhzPnvQEroOTgh8P0LTjxwFZG6BtVF5wfv4UGyUF3FxZmTxhIy0dRCYQ/sYkqKxN5BK7H5KmTAVjxwak/4wqmDz7zghNdtlNRgP0Vn7f5PhLhTe48AeP6H2HN3hOD80/MxA1Bk3Qipk7+1kBg+vYM5Elne58NzhrfHiUyFqzAU9o9qHS/M30AU7sOoLbVAXX5AyjiBIyPdczmOoeeviuAOtqXoaGP7yv2U/hgWMswcywoTw9O9wSuzNZg/swpA3MqKG3gRi9OGp9E4RpjmI9aTMK3bxguOA3dt8Cagh9nYsGqB6H91VOeN6plU9D1yu/RirkoX7sY2RFieHAZ3AoUIFmgRlyPAy6N1prwvvvSiwtO63NYJH1GsaUdvd3v4/cNVkC6xHjH93Bj1PVcQPsr/80TELVVqDMdhMV+ceDyTdTlyJhQNQ/LSxZ6L6EeweEmMxzIR8mDtyOLR5OM0GOhqFOwdYV8Btb1/9Bz+msAkzF18vUxIYzXzMJt7hzeYBs2t+9NrHQHwYLLQrjPIoX/b+gK7GgCmnTl9lU84Q6IOlTV/REHLHb0+29BhG2ITDuVUN28FCU6tecSquU/0CS91qiX4cEl06MI5jI1I42K4cvYiAdzAnJWVcAgfezCsR0PPf483ml3QnXzA6gpAxoW5+KGaSu9l1F8lxiV+NbkTM+S7Hda8FG3dL/hEhwtRvxmb+Bp3cAZpnrWrSha8UPk33gG75veke/kL+b+T0D2wrugky6h1j2Nbe4JqENRQWbMJTHDGBUYPwO3rJTuTVvRUN+Ad9p7vRC9aD+w13PpD7OQO00VG9CN38MdUnDAITTs+d9wuO8sSGdwa6CRvkijyIh2l+8WAPBZ7QvYe1KqW5p7T2ORlEazES2h9xSHbYULzq4OtEnp1N/FrUXLcW/+3+Kr99/EwcDpPGw5cSZQzsTC+z1vVOs2bEeDA1CXLEEB7+/HBcqgGBdbSCZVAda9uB16KS7ufQq63BugGKdBQdmv0OpPqobWUIFVOdJlFCVUuQVY6r4JvxMrp10HheI6aBa/AWjdq1u8uTKQe+t/8SyqMa7EtHEKKMZNw+L3LkGKwRh0T9FfWcQHykmZnoU2n1Wi4BoFsmusCP1OEXdm5beQOVuqpBWVBZOgyK7xfwOOMnsx1pbPBT5sRauDC2wiYvOJCAJToP3JRvciFP98kQKS4gbkrtzuXSjzMJbGejlemYNV2yqhhQOt23XQSPNFcQNu8p7BVW8oQrZSugWwGlv1cwGHEWtuusE79/7FfclRv3U1FgwTTAbPoY8xYcj5HM09xQhUAbsH1+ubuxOQXfQAytUOfNj6IRxcYBOgFvtDBsXYzcLkUEI1pxT17TY0/9HgDo7+RGo9DP8q7XOg9aAJJqvDvWpTmXUPtr7h/WC/lFi6PNq8C5vvDvzw/LXIWvEzvLGnClp3gWpoq/bC8ur/xON3zgYGLQrw1xrxgTJ7KbbU6r0fHFZjOvoRdgmAchaWbvnZQF+mjwMueBf1KKdjyYPLvGX4zn4jVsknKDBIQJlVjN1WC0wG37HoTSLNgwNvYP/WOz0LZQblHGqHEqr89dhvMcEgBT3vj1pvgMmyB1sLszyXE1VzUb7ThOY637ySzvD0MJhN2Fk+F8Odn4abQ5fCzOc9ln/DvseXeM6Im47Ddz7sa1esf8PV65u7yqzb8aB7ZTi4wCZW2JD0CumzKCH73JvS93ZGeCpccu4bTsDZjnde+iUe/fRevLe7OMXvvwUsKtDVwfZWOXL49mq4IyDoec6vIA5ujFTAvyDvL9DVteCt8jlj/n5ivHOMQXGkB+OYyi99WfMirPTf98xHVfPbeLZwyphSkKOz8U5YOepmGWkk4GhEqWYl9vq6pK5G88mtKBzmErAveTr/jXeO8f19Oh8VsvftbzAjz3d5V4cq0z5sZkCUXZkFUiBqAd/HrqQM0of/W3/KgBg1XviEPFMM78K9FBhVgXjfxY5qo1g4BdJIIN45xjPFNDoI2BUKUIACFBiZAIPiyPyYmwIUoAAF0kiAQTGNBpNdoQAFKECBkQkwKI7Mj7kpQAEKUCCNBBgU02gw2RUKUIACFBiZAIPiyPyYmwIUoAAF0kiAQTGNBpNdoQAFKECBkQmE/Udm0uc7pB/f35FVwdwUoEA4Ac6vcCrcR4HECoQNitJ3nsb7wcfEdoe1UyA1BDi/UmOc2MrUFYj3TScvn6bumLPlFKAABSggswCDosygLI4CFKAABVJXgEExdceOLacABShAAZkFGBRlBmVxFKAABSiQugIMiqk7dmw5BShAAQrILMCgKDMoi6MABShAgdQVYFBM3bFjyylAAQpQQGYBBkWZQVkcBShAAQqkrgCDYuqOHVtOAQpQgAIyCzAoygzK4ihAAQpQIHUFGBRTd+y8Lb8ER8vTWKRQQLOmEd2ulO8QO0CBqy/gPIKaRbdhQ8vZkLovwWFtwIZFGvdXXyoUGizasBuvWR0IO9WcJ2AszXOn1ZTuxBHHpeDypHpKfw2rM2zu4LTcSogAg2JC2OWr1NX9Fn7T+gPsv9yJHTiIpo4L8hXOkiiQ0gJOWGvuQWnjl0P3wnkC9Vu2499aLw5K5+p+E5uW7QPKDsDeLyD6rXh26iE8uuw3aO0NDWxn0bKlDJvGP42u/vNoueMoVpTtQ7s/2SV0m03ouPde3KziS+8g7CTZwZFJkoGIrxkX0PHun7GkYjHU47PwD3dn4VzflfiKYi4KjDkB71ng+hbctOqHUA3q/wV0NP0rjHn3Y03JAqilV0ulGgueqMbWvPfQZDkXnKP3OJoagJIHb0eWMgM5C29DnvltHPK9Ue09hJ3mW7F5xQzwhTeYLpm2ODbJNBoxt2UCckofRmEGhzFmOmYY8wKu9n0oqziFomfWoWDSuDAeTnTZTkE9fyamBk4x5RTMnH8RDU3H0RuQy3W6E8ccATvcD0/B1uUE0APrb19H5sOFyAosKzQ5txMuwOFJ+BDI1ADnSbz12mGcOc/LpzKJspg0F1Bq7sGeNzajUH1t+J66zqLzmD38cwAcxzpx2n9pFFBOnYn56tDks5A7TQVXdwt2n1uOR/InhybgdpIJMCgm2YDE15weWF/6Kdbs/Qyne76JrwjmokDKC3yJxtJs74IYBRSKSSioPIi9K78TsE+B7Bor3DcZVH8H9VD39px22NoGnfpFVsqYh6ISoOH376PbdQmOE0fRprsLC7OdaN1pgW79QqgcH+A590IcacFOI9q54CayZ4KeYVBMELx81brgtP4OFZUnodVOl69YlkSBlBOYjuL6Dkj/JN3z2weL4W7oTV8E7BPoqMhH2P+uPuL+TkHh5n3YMWUXpo27Dt9/7SYc2LMamo/3oz5zBXRqBw5segKv59WhT3yCmm8bod3SGnQJdsRNYAEjFmBQHDFhYgtwdR/AE8uegq38GezcqB2lyZ7YPrJ2CiREQKVBbt6g66FDN0U1B8XPNrmDsL1+PRbc+BXMu/tQ+kgBJnY0Y5dxFkqWz4MKGfjuLfOAhndhGbSKdegq+OzoCjAojq7v6Jbu+hwHfv4LGHNr8cbzxcjJ/BtcM7o1snQKjB0B94IaTcT+DlqAMyjlJXQfeAFm3UPQZgDOrg60haZxdKDzdMhnGUPTcPuqCjAoXlVuOSuTJpwBjxlnwFDzY+SH3BtxtddjnfFk+A8Yy9kMlkWBtBVQYVrurEELauBegNODvFxNmI9xBGA4j+EPr2XhYd10KKGEalo28gKedj9UZ2Pm1AgLfULTcvuqCDAoXhVmuSuR7iPuxEMr38Oddc9gnX9F2yV8cPA/0X2lG637uqArmsXPQ8lNz/JSSECF/Io3UV8c7732CcguegDlbc/hl3tOQPpgBVwOHHl+Oza1rcKGf8wZYn5dQPsrRpwpXe1/w6rM/gHu1x1Fw+vH4UQv/nT0OFCyBAX8SFVSHVMMikk1HFE2xmnBSxUG2Mqfxrayuf53q+Nzb0fpqccw7ZpyvKstw4osvgONUpTJ0kIgdPWptAJ18K9/9WkUfVZmLcGGfU9iaoMOk6Syxmmw4lgedrzxOLRDBDNX9/9C7REdfqKdMlCLcg7K9tRjedsaTFJ8DxVnytG6WYuMgRR8lAQCCiEt0wrzIx1MEZ4Kk5q7KECBWAQ4v2LRYloKxC4Q7xzjmWLs1sxBAQpQgAJpKsCgmKYDy25RgAIUoEDsAgyKsZsxBwUoQAEKpKkAg2KaDiy7RQEKUIACsQswKMZuxhwUoAAFKJCmAgyKaTqw7BYFKEABCsQuwKAYuxlzUIACFKBAmgowKKbpwLJbFKAABSgQuwCDYuxmzEEBClCAAmkqEPbfiknfBCD9+P6mad/ZLQokVIDzK6H8rJwCYQXCBkXp693i/YqcsLVwJwUoECTA+RXEwQ0KyC4Q75tOXj6VfShYIAUoQAEKpKoAg2KqjhzbTQEKUIACsgswKMpOygIpQAEKUCBVBRgUU3Xk2G4KUIACFJBdgEFRdlIWSAEKUIACqSrAoJiqI8d2U4ACFKCA7AIMirKTskAKUIACFEhVAQbFVB05tpsCFKAABWQXYFCUnZQFUoACFKBAqgowKKbqyLHdFKAABSgguwCDouykV6lA1+doXJMHRZER7a5wdbrgPFmPUo0Gi2qOwBkuCfdRgAIUoECQAINiEEcKbSinQ/fP5dCaX0Bd69lBDXc5mrHt0Wrsza1EzboCqAal4A4KjAEBlwPW+g1YpFC4v89ZoSjCBuObsDouDd35KPO52o0o8pftq0MR/s2q8wSMpXnudmhKd+JIaBucR1BT+mtYnWHf5Q7dXj4rmwCDomyUV7sgJVQ3F+Px8ov41ZaG4Ink+hwHNj2F7bZimPatR76Kw3y1R4f1XS0BJ6w196C08cswFV5C94FfYtkeoMxiR78Q6Lf/HFPfq8ay/3EIvWFyeHZFm88FZ1cH2nR1sPULSP9Iwf/bVI6coGl3Fi1byrBp/NPo6j+PljuOYkXZvoCrPJfQbTah4957cTPna8SRuRpPBA3b1aiQdcgooJyBFRuehK7ViBfMX8Lz/rIH1tr1WGkEyndUYkXWtTJWyKIokEICrlNo2vU28kp+jJJ8NaQXO6X6NjzxsyeR1/AuLL0RzsiizncOliYzMH8mpg73Stp7HE0NQMmDtyNLmYGchbchz/w2DnVc8ID2HsJO863YvGKGu50ppJx2TR1uKNOuw+nWIWXOcmyoug7G3zTiY+cVOK2/Q0XlUWira7GVEyzdhpv9iUXAaYetbTLmz5wSFGiUU2diPsxospwLX1q0+Vxn0XmsB3m5mmFvT7hOd+KYI7S6U7B1SXf7e2D97evIfLgQWXxFDkW66tscgqtOLneFU6Bd88+es8VX/oAdFQa0aitRs3Ex1BxdubFZXgoJhA9Evg7YcazzrPfqim+f52/U+dzB83pM/fPL+LHGez9RU4qaRiscISeh7kCsDq4HmIXcaSq4uluw+9xyPJI/OTQBtxMgwJfNBKDLXaUypxjbDDNgXKNHtW0p6l5cw/uIciOzvCQR+BKNpdneRTNSIJqEgsqD2LvyOwH7FMiu+U/0SPf7Ym619z5hFPk8wVODrAX/hN/ZvfcT26sx6/AvsLo2ZMV3xjwUlQANv38f3a5LcJw4ijbdXViY7UTrTgt06xdC5fgAz7kX4miwaEMj2rngJopRkD8Jg6L8pgkoMQPfvWUe1JiL8h0/R9mcjAS0gVVS4GoITEdxfcfAghbRB4vhbuhNXwTsE+ioyMf4UW6OMqccTaIJ2wqzBi7PqnKwpGgebJU1eKXde7/Q3Y4pKNy8Dzum7MK0cdfh+6/dhAN7VkPz8X7UZ66ATu3AgU1P4PW8OvSJT1DzbSO0W1qHWAw0yp0bw8UzKKbV4N+E2+beODBB06pv7AwFYhFQQjUtG3mxZHGnjTefryJfft/9Qt9+AKo5KH62yR287fXrseDGr2De3YfSRwowsaMZu4yzULJ8HlTwvMnFUIuBAorlQ3kFGBTl9UxQaZ5VcA735ZgJCWoDq6VAcgmEv4/na6Nm0AIc3zPx5vPlj+6v9LGPF2DWPQRtBjwf7QjN6OhA5+lhPk8ZmofbIxZgUBwxYRIU4F4FZ4c6mqXhSdBcNoECV0VApUFuXs+gBTWee4GeRS5h2xFVvgtoN66CQrMRLUEf7fDek1TrUFSQGbZ4907nMfzhtSw8rJsOJXxnlyHJ1dmYOZUfqQpRGfVNBsVRJx79ClwdH+JlswYlRfPAu4mj780akklAhfyKN1FfPH1wo5SzULT2LrRtMmDPSc9H9V2OD/D8L59DW9U6/GNOhKsqUeWbgJxVFTDkmlH/6icDX6Po/ASv1n+EpTvWQpsR6eX1AtpfMeJM6Wr/gjhl9g9wv+4oGl4/Did68aejx4GSJSiIWMbg7nKPTAIiwg8gXfrmDwUoMBoCnF/xqn4hTPrZQvIb6ne2wSIuS1X02URzXZXQ+tPPFXqDSVjsF/0N6LfVCR0g1FXN4rxvbxT5pKT9doswGfRC7StfWyXqmm2iz1dOmL/9XSaxdq1JdPUHP9lvPyRq9XMFoBbaKpOw9YUkCE7OrWEE4p1jCqnccPFVoVC4bwiHe477KECBkQlwfo3Mj7kpMJxAvHMs0vn9cPXxeQpQgAIUoEDaCTAopt2QskMUoAAFKBCvAINivHLMRwEKUIACaSfAoJh2Q8oOUYACFKBAvAIMivHKMR8FKEABCqSdAINi2g0pO0QBClCAAvEKMCjGK8d8FKAABSiQdgIMimk3pOwQBShAAQrEK8CgGK8c81GAAhSgQNoJhP2XY9I3AUg/vr9p12t2iAJJIMD5lQSDwCZQIEQgbFCUvvkt3q/ICSmfmxSgQBgBzq8wKNxFARkF4n3TycunMg4Ci6IABShAgdQWYFBM7fFj6ylAAQpQQEYBBkUZMVkUBShAAQqktgCDYmqPH1tPAQpQgAIyCjAoyojJoihAAQpQILUFGBRTe/zYegpQgAIUkFGAQVFGTBZFAQpQgAKpLcCgmNrjx9ZTgAIUoICMAgyKMmKyKApQgAIUSG0BBsXUHj+2ngIUoAAFZBRgUJQRk0VRgAKpLeBqN6JIoXB/zaX0NWH+3yIj2l2hfevFSeMaaKR0mlI8d8SB4CQ9sNb8V9RYe0IzcjuJBRgUk3hw2DQKUEBmgStW1GSvQ6PjSpiCXXB2daBNVwdbv4D0HdD+36Zy5AS9WrrQ2/IMCjddjx1d36CvpRDHVjyBPe0X/OW6uluwu+N2/Ojmyf59fJD8AkHDnPzNZQspQAEKjJbAOViazMD8mZg67CujN21JMZZkTYAq51bckXcULx/q9J4tnkXrTgt0m+9B1rBljVZ/WG48AhyueNSSJU9vCzZoAi7xDHu5J1kaznZQIAkFXGfReawHebkaqIZrnjutPSTV12iz2eGEC07rftRnroAu69qQNNxMdgEGxWQfoaHal1GIZ+0Bl3jEX2Ex3A1Ah+oNRcjm6A6lx+coECzgtMPWdj2m/vll/Nj3ZlNTippGKxzBNwsB5RTMnK8Jzo+JnoDq+hLm3X0ofaRg+OAaUgI3Ey/Al83Ej4FMLbgER8vzqKj8HPq6/46NhVng4MpEy2JSV8DRiNLAKyjXFKDys11YqblmYBGNYhFqrE64TnfimEODrAX/hN/53my2V2PW4V9gde0ROIMUMlFQpAMaGvFu9yW4HJ/gg7ZbcP/C78DZug9m3UPQqr7CkedKPQtxFm1EY3tvUAncSFIBEeEHkO4x8yc1BPpF36d7hF6tFtpqs7D3p0arx3IrOb8SNPqXLcIwe60w2S9H2YB+cb65Wqhxn6izfROS57ywmaqFFhBQ60XtYbvo7zssDPrnhaXvG9FlWi/U2lph6bss+iy1QquuFs3nOTlDEEdtM945xpOJJH2zEkuzXI5mbHu0Gu/cuR0vblwMNUc1Fj6mpcAQAkqopmUjD6dg6wo+VwQykFO8Df8urVK11+PJBX8Lh/kAzpWuRv7ETjTteht5JUtxs2o8VN/9eyyAGU2Wc0PUxaeSQYAvn8kwCiNpg/ME9vz0KWzHWux75keYo+KQjoSTeSkQr4Cr+01sMRdgvXYK4L4/+XVIUXYc6zwb8lnGkCTcTLgAX0ETPgQjaIDrczQ+8SOseWcB6l58EoVqrnQbgSazjmmBC2g3roJCsxEtvYGraryfXVTrUFSQOYRQDz7+w/vIfrjQ8xEMlQa5eRND0mswf+YU3usPUUm2TQbFZBuRqNvTA2vteqw0AuU7fo6yORlR52RCCoxZgfH5qOh4CcXq8SEEE5CzqgKGXDPqX/1kYFGN8xO8Wv8Rlu5YC21G5JdLV3sjfnFmOR7J935QXzkTC++/BeaGt/Cx8wqcf/o/OILhAmtIk7iZEIHIo5yQ5rDSaAWkSbix8iCAEzCunIlxgSvswn4lVbQlMx0F0kggdPVp4DzxP/asPoVqAZ7avwv3njMgx/fcsgagdBeeL54R+QzP9TkO1NpQ/pOFGHhrOgE5Zc/j8PJjWDbpGkyqOIPHW3+KwiECaxqpp3RXFNLSn3A9kL7zL8JT4ZJzHwUoEIMA51cMWExKgTgE4p1jPFOMA5tZKEABClAgPQUYFP4CTNcAAAE5SURBVNNzXNkrClCAAhSIQ4BBMQ40ZqEABShAgfQUYFBMz3FlryhAAQpQIA4BBsU40JiFAhSgAAXSU4BBMT3Hlb2iAAUoQIE4BBgU40BjFgpQgAIUSE8BBsX0HFf2igIUoAAF4hBgUIwDjVkoQAEKUCA9BRgU03Nc2SsKUIACFIhDIPRbcd1FSF+PI/34/sZRLrNQgALDCHB+DQPEpymQAIGwQZHfeZqAkWCVFKAABSiQcAFePk34ELABFKAABSiQLAIMiskyEmwHBShAAQokXIBBMeFDwAZQgAIUoECyCDAoJstIsB0UoAAFKJBwAQbFhA8BG0ABClCAAskiwKCYLCPBdlCAAhSgQMIFGBQTPgRsAAUoQAEKJIsAg2KyjATbQQEKUIACCRdgUEz4ELABFKAABSiQLAL/H4gWdJpWNEEUAAAAAElFTkSuQmCC"></p>
<p style="text-align:left;">What is the percentage uncertainty in x?</p>
<p style="text-align:left;">A. 5 %</p>
<p style="text-align:left;">B. 15 %</p>
<p style="text-align:left;">C. 25 %</p>
<p style="text-align:left;">D. 30 %</p>
</div>
<h2 style="margin-top: 1em">Markscheme</h2>
<div class="question">
<p>B</p>
</div>
<h2 style="margin-top: 1em">Examiners report</h2>
<div class="question">
<p>This question was well answered by candidates, as shown by a high difficulty index.</p>
</div>
<br><hr><br><div class="question">
<p>Four particles, two of charge +Q and two of charge −Q, are positioned on the <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi></math>-axis as shown. A particle P with a positive charge is placed on the <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>y</mi></math>-axis. What is the direction of the net electrostatic force on this particle?</p>
<p style="text-align:center;"><img src="data:image/png;base64,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"></p>
</div>
<h2 style="margin-top: 1em">Markscheme</h2>
<div class="question">
<p>D</p>
</div>
<h2 style="margin-top: 1em">Examiners report</h2>
<div class="question">
[N/A]
</div>
<br><hr><br><div class="question">
<p>The uncertainty in reading a laboratory thermometer is 0.5 °C. The temperature of a liquid falls from 20 °C to 10 °C as measured by the thermometer. What is the percentage uncertainty in the change in temperature?</p>
<p>A. 2.5 %</p>
<p>B. 5 %</p>
<p>C. 7.5 %</p>
<p>D. 10 %</p>
</div>
<h2 style="margin-top: 1em">Markscheme</h2>
<div class="question">
<p>D</p>
</div>
<h2 style="margin-top: 1em">Examiners report</h2>
<div class="question">
<p>Many candidates failed to recognize that the uncertainty in this error propagation question would affect both the initial and final temperature readings. The most common answer (option B) was incorrect, and only a minority of students correctly selected option D.</p>
</div>
<br><hr><br><div class="question">
<p>What is a correct value for the charge on an electron?</p>
<p>A. 1.60 x 10<sup>–12</sup> μC</p>
<p>B. 1.60 x 10<sup>–15</sup> mC</p>
<p>C. 1.60 x 10<sup>–22</sup> kC</p>
<p>D. 1.60 x 10<sup>–24</sup> MC</p>
</div>
<h2 style="margin-top: 1em">Markscheme</h2>
<div class="question">
<p>C</p>
</div>
<h2 style="margin-top: 1em">Examiners report</h2>
<div class="question">
[N/A]
</div>
<br><hr><br><div class="question">
<p>Which is a correct unit for gravitational potential?</p>
<p>A. m<sup>2 </sup>s<sup>−2</sup></p>
<p>B. J kg</p>
<p>C. m s<sup>−2</sup></p>
<p>D. N m<sup>−1 </sup>kg<sup>−1</sup></p>
</div>
<h2 style="margin-top: 1em">Markscheme</h2>
<div class="question">
<p>A</p>
</div>
<h2 style="margin-top: 1em">Examiners report</h2>
<div class="question">
[N/A]
</div>
<br><hr><br><div class="question">
<p><span style="background-color:#ffffff;">A proton has momentum 10<sup>-20</sup> N s and the uncertainty in the position of the proton is 10<sup>-10</sup> m. What is the minimum <strong>fractional</strong> uncertainty in the momentum of this proton?<br></span></p>
<p><span style="background-color:#ffffff;">A. 5 × 10<sup>-25</sup><br></span></p>
<p><span style="background-color:#ffffff;">B. 5 × 10<sup>-15</sup><br></span></p>
<p><span style="background-color:#ffffff;">C. 5 × 10<sup>-5</sup><br></span></p>
<p><span style="background-color:#ffffff;">D. 2 × 10<sup>4</sup></span></p>
</div>
<h2 style="margin-top: 1em">Markscheme</h2>
<div class="question">
<p>C</p>
</div>
<h2 style="margin-top: 1em">Examiners report</h2>
<div class="question">
<p>Over 100 candidates left this blank. It is testing fractional uncertainty and also involves the Heisenberg uncertainty principle.</p>
</div>
<br><hr><br>