Question

In shown situation elevator is moving upward with acceleration of $5m/s^2$

Column I		Column II
1	Net force acting on B	P	150 N
2	Normal reaction between A and B	Q	300 N
3	Normal reaction between B and C	R	450 N
4	Normal reaction between C and elevator	S	750 N
		T	1500 N

• A. (1)-P (2)-Q (3)-S (4)-T
• B. (1)-Q (2)-Q (3)-R (4)-T
• C. (1)-P (2)-R (3)-S (4)-S
• D. (1)-Q (2)-R (3)-R (4)-T

Answer 1

Answer: (A)

For (1) : Net force on $B=ma=(30)(5)=150N$
For (2) : FBD of $A$

$N_{AB}-20g=20(5)\Rightarrow N_{AB}=300N$
For (3) : FBD of $B$

$N_{BC}-N_{AB}-30g=30(5)$
$\Rightarrow N_{BC}=750N$
For (4): For system of $A+B+C:$
$N_C-100g=100(5)$
$\Rightarrow N_C=1500N$