Forces Quiz

🚀 Newton’s Laws of Motion

1. First Law (Inertia): Objects stay at rest or move at constant velocity unless acted on by a net force.

2. Second Law: Fnet=maF_{\text{net}} = maFnet​=ma (Net force = mass × acceleration)

3. Third Law: Every action has an equal and opposite reaction.

🧮 Key Equations

• Weight (Force of Gravity): Fg=mgF_g = mgFg​=mg

  • mmm = mass (kg)

  • g=9.8 m/s2g = 9.8 \, \text{m/s}^2g=9.8m/s2 (gravity)

• Friction: f=μNf = \mu Nf=μN

  • μ\muμ = coefficient of friction

  • NNN = normal force

• Normal Force (N):

  • On a flat surface with no vertical forces: N=mgN = mgN=mg

  • On an incline: N=mgcos⁡θN = mg \cos \thetaN=mgcosθ

• Forces on an Incline:

  • Parallel to incline: F∥=mgsin⁡θF_{\parallel} = mg \sin \thetaF∥​=mgsinθ

  • Perpendicular to incline: F⊥=mgcos⁡θF_{\perp} = mg \cos \thetaF⊥​=mgcosθ

• Tension (T):

  • If object is at rest or moving at constant speed vertically: T=mgT = mgT=mg

  • If accelerating: T=mg+maT = mg + maT=mg+ma (if upward), T=mg−maT = mg - maT=mg−ma (if downward)

• Components of a Force at an Angle:

  • Horizontal: Fx=Fcos⁡θF_x = F \cos \thetaFx​=Fcosθ

  • Vertical: Fy=Fsin⁡θF_y = F \sin \thetaFy​=Fsinθ

• Kinematics (if needed):

  • v=v0+atv = v_0 + atv=v0​+at

  • d=v0t+12at2d = v_0 t + \frac{1}{2}at^2d=v0​t+21​at2

  • v2=v02+2adv^2 = v_0^2 + 2adv2=v02​+2ad

📝 Quick Rules to Remember

✅ Constant velocity → net force = 0 (forces are balanced)
✅ Acceleration → net force ≠ 0 (use Fnet=maF_{\text{net}} = maFnet​=ma)
✅ Normal force decreases if you pull upward at an angle and increases if you push downward.
✅ Friction always opposes motion.
✅ On an incline, gravity pulls the object down the ramp, not straight down.