Alex, who has a mass of 100 kg, is skateboarding at 9.0 m/s when he smacks into a brick wall and comes to a dead stop in 0.2 s. a. show that his deceleration is 45 m/sz. b. show that the force ofimpact is 4500 n. (ouch! )

A. The deceleration of Alex is 45 m/s²

B. The force of impact is 4500 N

From the question given above, the following data were obtained:

a = (v – u) / t

a = (0 – 9) / 0.2

a = –9 / 0.2

a = –45 m/s²

The, negative sign indicate that the Alex is coming to rest.

F = ma

F = 100 × 45

F = 4500 N

Learn more about acceleration:

link

Part a)

acceleration is defined as rate of change in velocity

so we can write

here we know that

finally it will stop so vf = 0

initial speed is given as 9m/s

and the time to stop is 0.2 s

Part b)

Now by 2nd law of Newton

given that

m = 100 kg

a = 45 m/s^2

so now using above equation

so it will exert 4500 N force to stop

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.