Newton's Second Law Physics Example 2

Follow the full solution, then compare it with the other examples linked below.

Example 2

medium
A 1200 kg1200 \text{ kg} car accelerates from rest to 20 m/s20 \text{ m/s} in 8 seconds8 \text{ seconds}. What net force is required?

Solution

  1. 1
    Find the acceleration using the definition a=ΔvΔta = \frac{\Delta v}{\Delta t}, where Δv=20−0=20 m/s\Delta v = 20 - 0 = 20 \text{ m/s} and Δt=8 s\Delta t = 8 \text{ s}.
  2. 2
    Calculate: a=208=2.5 m/s2a = \frac{20}{8} = 2.5 \text{ m/s}^2
  3. 3
    Apply Newton's second law to find the force: Fnet=ma=1200×2.5=3000 NF_{\text{net}} = ma = 1200 \times 2.5 = 3000 \text{ N}

Answer

Fnet=3000 NF_{\text{net}} = 3000 \text{ N}
Newton's second law connects force to the rate of change of velocity. A heavier car needs more force to achieve the same acceleration as a lighter one.

About Newton's Second Law

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass, with the acceleration pointing.

Learn more about Newton's Second Law →

More Newton's Second Law Examples

Example 1 easy

A [formula] cart is pushed with a net force of [formula]. What is the acceleration of the cart?

Example 3 hard

A [formula] block on a frictionless surface is pulled by a [formula] force at an angle of [formula]

Example 4 medium

A [formula] truck accelerates at [formula] while resistive forces total [formula] opposite the motio

← All Newton's Second Law Examples Newton's Second Law Concept