Question

A $20\text{kg}$ wagon originally at rest, is pushed with a force of $7\text{N}$ for $1.5\text{s}$, then with a force of $5\text{N}$ for $1.7\text{s}$ and then with a force of $10\text{N}$ for $3\text{s}$. Find the final velocity of the cart.

• A. $2.45\text{m/s}$
• B. $3\text{m/s}$
• C. $4.5\text{m/s}$
• D. $5.5\text{m/s}$

Answer 1

The correct option is A $2.45\text{m/s}$

We know that
Impulse = Force $\times$ time
Total Impulse $=F_1{t}_1+F_2{t}_2+F_3{t}_3$
$=7\times 1.5+5\times 1.7+10\times 3=49\text{kg m/s}$
Now, change in momentum = Total impulse
$\Rightarrow 20\text{kg}\times (v-0)=49\text{kg m/s}$
$v=2.45\text{m/s}$