Complete Question:
One simple model for a person running the 100 m dash is to assume the sprinter runs with constant acceleration until reaching top speed, then maintains that speed through the finish line. If a sprinter reaches his top speed of 11.5 m/s in 2.24 s, what will be his total time?
Answer:
total time = 6.24 s
Explanation:
Using the equation of motion:
v = u + at
initial speed, u = 0 m/s
v = 11.5 m/s
t = 2.24 s
11.5 = 0 + 2.24a
a = 11.5/2.24
a = 5.13 m/s²
For the total time spent by the sprinter:
s = ut + 0.5at²
100 = 0.5 * 5.13 * t²
t² = 100/2.567
t² = 38.957
t = √38.957
t = 6.24 s
Answer:
(a) The elevator has an acceleration of 2.14 m/s² and direction is downward
(b) The acceleration is a=2.14 m/s²
Explanation:
Let +y be upward direction
For Part (a)
The mass of student (whose weight is 550N) is:
ms=w/g
ms=550/9.8=56.1 kg
Apply ∑Fy=ma

Solve for acceleration a

The elevator has an acceleration of 2.14 m/s² and direction is downward
Part(b)
For the acceleration is the scale reads 670 N
For n=670N
So

Answer:
Acceleration due to gravity