Question

A 3 kg cart starting from rest on a frictionless surface is pulled by a horizontal mass-less rope with a constant force of 6 N. What is the acceleration of the cart, and how fast is it moving at the end of two seconds?

Answer 1

We know that $F = ma$. So, we can find acceleration: $F = ma \Rightarrow a = \frac{F}{m} = \frac{6N}{3kg} = 2\frac{m}{s^2}$.

And we know that a cart starting from rest, so, the velocity in the beginning of the motion is equal to the zero: $v_0 = 0$. And we know acceleration. So, we can find the velocity after 2 seconds of the motion:

$$v_2 = v_0 + a \cdot t = 0 + 2 \cdot 2 = 4 \frac{\mathrm{m}}{\mathrm{s}}.$$

Answer: acceleration is $2\frac{\mathrm{m}}{\mathrm{s}^2}$; velocity at the end of two seconds is $4\frac{\mathrm{m}}{\mathrm{s}}$.