Physics 1 - 1D Kinematics (Skills)

How do you mentally calculate acceleration given initial velocity, final velocity, and time?

Use the formula a = (v_f - v_i) / t. Break it into steps: subtract initial velocity from final velocity, then divide by time. For example, 10 m/s to -32 m/s in 6 s: -32 - 10 = -42, then -42 / 6 = -7 m/s².

How do you find displacement mentally using average velocity?

Use s = [(v_i + v_f) / 2] * t. Add initial and final velocities, halve the sum, then multiply by time. For 10 m/s to -32 m/s in 6 s: 10 + (-32) = -22, -22 / 2 = -11, -11 * 6 = -66 m.

How do you determine distance mentally when given displacement?

Distance is the absolute value of displacement. After calculating displacement, take the positive value. For -66 m displacement: distance = 66 m.

How do you estimate time to travel a distance with constant acceleration mentally?

For s = ut + (1/2)at², approximate by testing reasonable time values. For 1.1 m/s, 0.2 m/s², 67 m: estimate t ≈ 20 s, compute 1.1 * 20 + 0.1 * 20² = 22 + 40 = 62 m (close), try t ≈ 22 s mentally to adjust.

How do you calculate time to the top for an object thrown upwards mentally?

Use t = v_i / g, where g ≈ 10 m/s² for simplicity. For 1.8 m/s: 1.8 / 10 = 0.18 s. Adjust for g = 9.8 m/s² by estimating slightly higher, around 0.184 s.

How do you find total time for an object thrown upwards and falling back mentally?

Double the time to the top. For 1.8 m/s with t_top ≈ 0.18 s: total time ≈ 0.18 * 2 = 0.36 s.

How do you mentally calculate initial velocity given displacement, time, and final velocity?

Use v_i = (2s / t) - v_f. For 125 m in 13 s, v_f = 14 m/s: 125 / 13 ≈ 9.6, 2 * 9.6 = 19.2, 19.2 - 14 ≈ 5.2 m/s.

How do you compute acceleration mentally using initial and final velocities and time?

Use a = (v_f - v_i) / t. For v_i ≈ 5.2 m/s, v_f = 14 m/s, 13 s: 14 - 5.2 = 8.8, 8.8 / 13 ≈ 0.68 m/s² (estimate by dividing 8.8 by 10 ≈ 0.9, adjust down).

How do you mentally calculate the sum of forces on an object?

Use F_net = ma. Identify the object’s mass and acceleration, multiply mentally. If forces are given, add same-direction forces and subtract opposite ones to find net force.

How do you mentally sum multiple forces acting on an object?

Assign a positive direction, give forces in that direction positive signs, opposite forces negative signs. Add them mentally: F_net = F₁ + F₂ + ... + Fₙ. Practice with small numbers to keep track.