Unit 2
5 marks · Normal1. Scientists measured the mass of a grain of rice as 0.000028 kg. In a laboratory, a student investigates a relationship using the formula , where is mass in kilograms and m/s.
Express the mass of one grain of rice in standard form.
Calculate and write your answer in standard form.
Using your answers to (a) and (b), work out the value of for one grain of rice. Give your answer in standard form.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 2.8 × 10^{-5}
(b) 9 × 10^{16}
(c) 2.52 × 10^{12}
Common mistakes: Forgetting powers of ten in multiplication; Incorrectly squaring
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correct conversion of 0.000028 to standard form as 2.8 × 10^{-5}.
M2 (b) · 1 mark · Squares 3 to give 9.
A1 (b) · 1 mark · Squares (10^8) to give 10^{16}, answer 9 × 10^{16} in standard form.
M3 (c) · 1 mark · Substitutes the numbers in E = mc^2 with their standard form values. (follow-through)
A2 (c) · 1 mark · Correct final answer E = 2.52 × 10^{12} in standard form. (follow-through)
Worked solution
a) 0.000028 = 2.8 × 10^{-5}
b) , so
c)