Question 3

Three blocks $$A$$, $$B$$ and $$C$$ are pulled on a horizontal smooth surface by a force of 80 N as shown in figure. The tensions $$T_1$$ and $$T_2$$ in the string are respectively:

Let us write equations for all three blocks A,B and C

For A:-

$$F-T_2=2a$$

$$80-T_2=2a$$

For B:-

$$T_2-T_1=3a$$

and For C:-

$$T_1=5a$$

Now on adding all 3 equations

We get $$80\ =\ 10a$$

$$a = 8 \text{ m s}^{-2}$$

now substitute value of a in equation 1

$$80-T_2=2a$$

$$80-T_2=2\times\ 8$$

$$80-16\ =T_2$$

$$T_2=64N$$

Substitute the value of a in equation 3

$$T_1=5a$$

$$T_1=5\times\ 8$$

$$T_1=40N$$

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