Question

The acceleration of a particle is defined by the relation a=-8m/s2. Knowing that x=20m when t=4 and that x=4m when v=16m/s. Determine. A)the time when the velocity is zero. B)the velocity and total distance traveled when t=11s.

Answer 1

wrong. Your equation x = -4t^2 + 16t + 36 gives
x(4) = 36, not x=20
it also gives v(0) = 16, but x(0) = 36, not x=4

Answer 2

A) To find the time when the velocity is zero, we need to find t when v=0:

a=dv/dt
-8 = dv/dt

Integrate both sides with respect to t:

∫-8dt = ∫dv
-8t = v + C

Given that v=0 when t=t0:

-8t0 = 0 + C
C = -8t0

Therefore, the velocity equation is:

v = -8t + C

Given that x=20 when t=4:

Integrate a=-8 to find v:

a = dv/dt
-8 = dv/dt
-8t = v + C
-8 * 4 = 16 = v + C
v = -8t + 16

Integrate v to find x:

v = dx/dt
-8t + 16 = dx/dt
-4t^2 + 16t + D = x

Given that x=20 when t=4:

-4(4)^2 + 16(4) + D = 20
D = 36

Therefore, x = -4t^2 + 16t + 36

Given that x=4 when v=16:

-4t^2 + 16t + 36 = 4

Solve for t to find time when velocity is zero.

-4t^2 + 16t + 36 = 4
-4t^2 + 16t + 32 = 0
t^2 - 4t - 8 = 0

t = (4 ± √(16 - 4(-8)))/2
t = (4 ± √(48))/2
t = (4 ± 4√3)/2
t = 2 ± 2√3

So, the time when the velocity is zero is t = 2 ± 2√3 seconds.

B) To find the velocity and total distance traveled when t=11s, substitute t=11 into the equations for v and x:

v = -8(11) + 16
v = -88 + 16
v = -72 m/s

x = -4(11)^2 + 16(11) + 36
x = -4(121) + 176 + 36
x = -484 + 212
x = -272 m

Therefore, when t=11s, the velocity is -72 m/s and the total distance traveled is 272m.

Answer 3

I apologize for my mistake. Let's correct it:

Given that x=20 when t=4:

-4(4)^2 + 16(4) + D = 20
D = 36

Therefore, x = -4t^2 + 16t + 36

Given that x=4 when v=16:

-4t^2 + 16t + 36 = 4

Solve for t to find time when velocity is zero.

-4t^2 + 16t + 32 = 0
t^2 - 4t - 8 = 0

t = (4 ± √(16 - 4(-8)))/2
t = (4 ± √(48))/2
t = (4 ± 4√3)/2
t = 2 ± 2√3

So, the time when the velocity is zero is t = 2 ± 2√3 seconds.

Now, let's find the correct equation for x:

x = -4t^2 + 16t + 36

When t=11s:

x = -4(11)^2 + 16(11) + 36
x = -484 + 176 + 36
x = -272 m

Therefore, when t=11s, the total distance traveled is 272m.

Now let's find the velocity when t=11s:

v = -8(11) + 16
v = -88 + 16
v = -72 m/s

Thus, when t=11s, the velocity is -72 m/s and the total distance traveled is 272m.