A block of mass m is in contact with the cart C as shown in the figure. The coefficient of static friction between the block and the cart is μ. The acceleration α of the cart that will prevent the block from falling satisfies (a) α > mg/μ (b) α > (g)/(μ m) (c) α ≥ g/μ (d) α < g/μ

Answer: (c). The cart pushes the block forward: normal force N = mα. Friction (upward) must balance weight: μ N ≥ mg μ mα ≥ mg ⇒ α ≥ g/μ So the answer is (c).

A block of mass m is in contact with the cart C as shown in the… | NEET 2010 (AIPMT, Prelims)

Q12NEET 2010 · AIPMT · PRELIMSEasy

Two-Body Friction

A block of mass m is in contact with the cart C as shown in the figure.

The coefficient of static friction between the block and the cart is $\mu$ . The acceleration $\alpha$ of the cart that will prevent the block from falling satisfies

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Answer: (c)

The cart pushes the block forward: normal force $N = m\alpha$ .
Friction (upward) must balance weight: $\mu N \ge mg$
$\mu m\alpha \ge mg \Rightarrow \alpha \ge \frac{g}{\mu}$
So the answer is (c).

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