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

By E-Code · updated

Press MATH, ▲ and ENTER for the Numeric Solver, type the formula as E1 = E2 (D = V×T+1/2×A×T²) and press GRAPH (OK). Type the values you know and a guess for the unknown, put the cursor on it and press GRAPH (SOLVE): D = 100, V = 5, A = 2 gives T = 7.81.

Step by step

  1. Open the MATH menu. MATH Press MATH. Its last item is the Numeric Solver.
  2. Jump to the bottom. ▲ Press ▲. The list wraps round to its last item, Numeric Solver.
  3. Open the Solver. ENTER Press ENTER. The solver takes an equation as two sides, E1 = E2.
  4. Type the left side. ALPHA X⁻¹ Take d = v·t + ½·a·t². Type the left side into E1: ALPHA, then x⁻¹ for D.
  5. Move down to E2. ENTER Press ENTER to move down to E2, the right side.
  6. Type the right side. ALPHA 6 × ALPHA 4 + 1 ÷ 2 × ALPHA MATH × ALPHA 4 X² Type V×T+1/2×A×T². ALPHA 6 is V, ALPHA 4 is T, ALPHA MATH is A, and x² squares the T.
  7. Press OK. GRAPH Press GRAPH, the key under OK. The solver lists every letter of the formula in order: D, V, T, A.
  8. Distance: 100 m. 1 0 0 ENTER A car covers 100 m. Type 1 0 0 for D and press ENTER to move on.
  9. Start speed: 5 m/s. 5 ENTER It starts at 5 m/s. Type 5 for V and ENTER.
  10. 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.
  11. Acceleration: 2 m/s². 2 It speeds up at 2 m/s². Type 2 for A.
  12. Back to T. ▲ Press ▲ to put the cursor back on T, the letter to solve for.
  13. Solve. GRAPH Press GRAPH, now the key under SOLVE.
  14. 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

Related

Physics programs for the TI-84 Plus CE:

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