A ball is thrown horizontally at 12 m/s from the top of a 45 m cliff. Ignoring air resistance and taking g = 10 m/s^2, what is its speed just before it hits the ground?
Answer and explanation
Correct answer: D. 32.3 m/s
- Step 1: Vertical speed after falling 45 m: vy = root(2gh) = root(2 x 10 x 45) = root 900 = 30 m/s.
- Step 2: The horizontal speed stays 12 m/s.
- Step 3: Speed = root(12^2 + 30^2) = root(144 + 900) = root 1044 = 32.3 m/s.
Answer
32.3 m/s.
Why not the others: 42.0 m/s adds the components arithmetically; 30.0 m/s is the vertical speed only; 36.0 m/s comes from using 6 m/s^2 for the vertical acceleration.
Practise more Physical and Chemical Principles.
Free questions with an explanation for every one, and full timed Jubilee Institute Admission Test mock tests.
More Physical and Chemical Principles questions
- A uniform rod of length 2.0 m and mass 6.0 kg is pivoted at one end. A vertical upward force F is applied at the opposite end to keep the ro…
- An aqueous solution of hydrochloric acid has a pH of 2.0. If 10 mL of this solution is diluted with pure distilled water to a final volume o…
- A car traveling at a constant speed of 20 m/s accelerates uniformly at 2.5 m/s^2 over a straight distance of 100 m. What is the final veloci…
- Which of the following electronic configurations represents a transition metal atom in its ground state according to Hund's rule and the Auf…
- Two point charges of +4.0 microcoulombs and -1.0 microcoulombs are positioned 0.30 m apart along a line in a vacuum. At what point along the…
- When 5.4 g of solid aluminum (molar mass = 27 g/mol) reacts completely with excess iron(III) oxide via the thermite reaction: 2Al + Fe2O3 ->…