Question

The figure shows the velocity - time graph of a ball of mass $20\text{g}$ moving along a straight line on a table. How much average force does the table exert on the ball to bring it to rest?

• A. $0.02\text{N}$
• B. $0.03\text{N}$
• C. $0.04\text{N}$
• D. $0.05\text{N}$

Answer 1

The correct option is C $0.04\text{N}$

Average force,

$F=\frac{\Delta p}{\Delta t}=\frac{p_f-p_i}{\Delta t}=\frac{m(v_f-v_i)}{\Delta t}$

$\Rightarrow F=\frac{20\times {10}^{-3}(0-20)}{10}=-0.04\text{N}$

Negative sign shows that friction force applied by the table acts opposite to the initial velocity.