In: Physics
Varible Force A 1.8 kg particle moves along an
x axis, being propelled by a variable force directed along
that axis. Its position is given by x = 3.0 m +
(4.0 m/s)t + ct2 - (2.2
m/s3)t3, with x in meters
and t in seconds. The factor c is a constant. At
t = 3.0 s, the force on the particle has a magnitude of 36
N and is in the negative direction of the axis. What is
c?
in m/s2
The particle is moving along x-axis and mass of the particle is given
m = 1.8 kg
Position with respect to time
x = 3.0m + (4.0m/s)t +ct2 _ (2.2 m/s3)t3
The first derivative of position with respect to time is velocity and it's second deriative is acceleration.
So taking first derivative with respect to time ,
Taking second derivative ,
acceleration a =
At time t =3.0s , force is given by
F = -36N ( negative sign is because the force is acting in negative x axis opposite direction of the motin of the particle)
hence, ma = -36N
a = -36/m
a = -36/1.8
= -20m/s2 ----------------(3)
we have acceleration interms of time from double derivative of position, so putting t =3 in equation 2 gives
a = 2c - 2.2m/s3*6*3 s
= 2c - 39.6m/s2 ----------------(4)
equating (3) and (4) gives
2c -39.6m/s2 = -20m/s2
2c =( -20+39.6)m/s2
2c = 19.6 m/s2
c = (19.6/2)m/s2
= 9.8 m/s2
Hence c is 9.8 m/s2