Question

A 1 kg block is attached by light string to another block of mass 2 kg. The string is passed over a pulley of negligible mass and friction. Calculate the acceleration of the masses?

• A. $5m/s^2$
• B. $6.7m/s^2$
• C. $10m/s^2$
• D. $20m/s^2$
• E. $30m/s^2$

Answer 1

Answer: (B)

$6.7m/s^2$

Let the tension in the string and acceleration of the blocks be $T$ and $a$ respectively.

For block of mass 1kg : $1a=T$ ..........(1)

For block of mass 2kg : $2a=2g-T$ ...........(2)

Adding both equations, we get $3a=2g$ $⟹a=\frac{2g}{3}=\frac{2\times 10}{3}=6.7m/s^2$