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How to solve a physics formula for any letter on a TI-84 Plus or TI-83 Plus

By E-Code · updated

Press MATH, ▲ and ENTER for the Solver, type the formula with 0 on one side (0 = V×T+1/2×A×T²−D) and press ENTER. Type the values you know and a guess for the unknown, put the cursor on it and press ALPHA ENTER (SOLVE): V = 5, A = 2, D = 100 gives T = 7.81.

Step by step

  1. Open the MATH menu. MATH Press MATH. Its last item is the Solver.
  2. Jump to the bottom. ▲ Press ▲. The list wraps round to the last item, Solver.
  3. Open the Solver. ENTER Press ENTER. The solver wants the equation with 0 on one side: eqn:0=.
  4. Type the formula. ALPHA 6 × ALPHA 4 + 1 ÷ 2 × ALPHA MATH × ALPHA 4 X² − ALPHA X⁻¹ For d = v·t + ½·a·t², move D across: type V×T+1/2×A×T²−D. ALPHA 6 is V, ALPHA 4 is T, ALPHA MATH is A, ALPHA x⁻¹ is D.
  5. Confirm it. ENTER Press ENTER. The solver lists every letter of the formula in order: V, T, A, D.
  6. Start speed: 5 m/s. 5 ENTER A car starts at 5 m/s. Type 5 for V and press ENTER to move on.
  7. Guess the time. 5 ENTER T is the one you want. Type a guess, 5 seconds, and ENTER: the solver starts there and finds the answer closest to it.
  8. Acceleration: 2 m/s². 2 ENTER It speeds up at 2 m/s². Type 2 for A and ENTER.
  9. Distance: 100 m. 1 0 0 It covers 100 m. Type 1 0 0 for D.
  10. Back to T. ▲ ▲ Press ▲ twice to put the cursor back on T, the letter to solve for.
  11. Solve. ALPHA ENTER Press ALPHA, then ENTER. SOLVE is written above ENTER.
  12. There's your time. T = 7.81 s. The ■ marks the letter it solved; left-rt = 0 means both sides match. Put the cursor on any other letter to solve for it instead.

What the screen shows

T = 7.81 s. The ■ marks the letter it solved; left-rt = 0 means both sides match. Put the cursor on any other letter to solve for it instead.

Look for T=7.807 on the screen.

Try it with the keys lit up

This guide is one of E-Code's Learn lessons. Open it on E-Code's TI-84 calculator and each key lights up in turn as you press it.

Try “Solve a physics formula for any letter” on the TI-84 calculator

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