Question #260548

A bus driver forgot to stop at a bus stop. Just as he passes the stop, he begins to decelerate 5 seconds later, the bus is 80m beyond the stop and has slowed to 10m/s.



a. Calculate the speed of the bus as it passed the bus stop.



b. What is the deceleration of the bus?

1
Expert's answer
2021-11-03T10:23:03-0400

Solution;

when a body moves along a straight line with constant acceleration or deceleration,the equations of motion that describe the body's motion are:

a=vfv0ta=\frac{v_f-v_0}{t} ......(1)

Where ;

a is acceleration or deceleration.

vf is the final velocity.

v0 is the initial velocity.

t is the time taken.

The displacement in one direction would be;

Δx=v0t+at22\Delta x=v_0t+\frac{at^2}{2} .....(2)

By substituting (1) into (2),Resolve to;

Δx=vf+v02t\Delta x=\frac{v_f+v_0}{2}t ......(3)

Given;

Δx=80m\Delta x=80m

vf=10m/sv_f=10m/s

t=5st=5s

a)

Calculate speed of bus as it passed the stop;v0v_0 ;

Using equation (3),by direct substitution;

80=10v02×580=\frac{10-v_0}{2}×5

32=10+v032=10+v_0

v0=3210=22m/sv_0=32-10=22m/s

Ans; 22m/s

(b)

Deceleration of the bus;

Using equation (1),by direct substitution;

a=10225a=\frac{10-22}{5}

a=2.4m/s2a=-2.4m/s^2

(Negative shows the bus is decelerating)

Ans;2.4m/s2




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