Answer: 4 s.
- A 1 s
- B 2 s
- C 4 s
- D Never
Correct answer: C. 4 s
Explanation: Vertical pos: P<sub>1</sub>=40-5t², P<sub>2</sub>=10t-5t². Equal: 40-5t²=10t-5t² → 40=10t → t=4 s.
On a velocity-time graph for uniform acceleration, the slope of the line gives the acceleration and the shaded area under the line gives the displacement.
Concept context
Equations of motion, projectile motion, relative velocity. Foundation of all mechanics.