Question

What horizontal force is required to pull a 6 kg sledge with a 4 m/s2 acceleration when a friction force of 20 N is against its motion?

Answer 1

The horizontal force required to pull the sledge is equal to:

F = 48 N

We apply Second Newton Law onto the sledge at the moment it is being pulled by an "F" force.

The friction force "Ff" is at opposite direction the acceleration, so it has negative sign and F force is at equal direction the aceleration and it has  positive sign:

• ∑F = m * a
• F - Ff = 6Kg * 4m/s²
• F - 20N = 24N
• F = 48 N