Question

Example 9.5 The velocity-time graph of a
ball of mass 20 g moving along a
straight line on a long table is given in
Fig. 9.9.​

Answer 1

Answer:

t= 10 seconds

(u ) initial velocity =20

(v) final velocity =0

m=20g convert into kg.

Explanation:

use formula: F =ma

F = m(v - u )/ t

put value and solve..

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Answer 2

$\huge\mathfrak\pink{Solution}$

The initial velocity of the ball = 20cm s¯¹.

Due to the frictional force exerted by the table, the velocity of the Bal decreases down to zero in 10s.

★ Thus:-

${ \ U \ = \ 20cm s¯¹}$

${ \ V \ = \ 0cm s¯¹}$

${ \ T \ = \ 10s}$

Since the velocity- time graph is a straight line, it is clear that the ball moves with a constant acceleration . The acceleration a is

‎

‎ ‎ ‎ ‎ ‎ ‎ ‎${ \ a \ =}$ $\frac{v - u}{t}$

$\tt{\implies}$ $\frac{(0cm s¯¹)}{10s}$

$\tt{\implies}$ ${ \ - 2 s¯²}$

$\tt{\implies}$ ${ \ - 0.02m s¯²}$

The force exerted on the ball F is

${ \ F \ = \ ma \ =}$ $\frac{20}{1000}$ ${ \ kg \ × ( - 0.02 m s¯¹)}$

${ \ = \ 0.0004 N}$

The negative sign implies that the frictional force exerted by the table is opposite to the direction of the ball.