3:31 PM bb9.stmarytx.edu No SIM 20% 11 of 11 Practice Problems 1. On the earth,

Question

3:31 PM bb9.stmarytx.edu No SIM 20% 11 of 11 Practice Problems 1. On the earth, when an astronaut throws a 0.250-kg stone vertically upward, it returns to his hand a time Tlater. On planet X he finds that, under the same circumstances, the stone returns to his hand in 2T. In both cases, he throws the stone with the same initial velocity and it feels negligible air resistance. The acceleration due to gravity on planet X (in terms of g) is A) g/4. B) g/2. E) 2g. If C = [10 m, 307 and D = [25 m, 1307, what is the direction of the sum of these two vectors? b. 73 c. 107 d. 163 e. 100 3. Under what condition is IA-BI A+B? A) The magnitude of vector B is zero. B) Vectors A and B are in opposite directions C) Vectors A and B are in the same direction. D) Vectors A and B are in perpendicular directions. E) The statement is never true

Explanation / Answer

1. Answer-B

Apply s=ut+at2/2 for the whole motion

in earth, 0=uT-gT2/2 ----(1)

in the planet, 0=u(2T)-g'(2T)2/2 ---(2); where g'-grvitational acceleration in the planet

From 1) and (2),

g'= g/2

2. these 2 vectors can be written in i,j basis

C= 10cos(30)i+10sin(30)j ; D=25cos(130)i + 25sin(130)j

C+D= -7.409 i +24.151 j

direction= tan-1 (24.151/-7.409 )= 1070

3. E.

Left handside is a scalar while the right side is a vector

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