course phy201
2/15/2010 8:47 pm
Week 2 Quiz 2Reason out the quantities v0, vf, Dv, vAve, a, Ds and Dt: If an object’s velocity changes at a uniform rate from 10 cm/s to 13 cm/s as it travels 46 cm, then what is the average acceleration of the object?
Using the equations which govern uniformly accelerated motion determine vf, v0, a, Ds and Dt for an object which accelerates through a distance of 46 cm, starting from velocity 10 cm/s and accelerating at
.75 cm/s/s.
Vo = initial velocity = 10 cm/ s
Vf= final velocity = 13 cm/s
Dv= vf- Vo = (13cm/s - 10 cm/s) = 3 cm/s
Vave= (vf + vo)/ 2
Vave (13cm/s + 10cm/s) / 2
Vave = 11.5 cm/s
ds=46cm
dt= ds/vave
dt= 46cm / 11.5 cm/s
dt= 4 seconds
aAve= dv/dt
aAve= 3cm/s / 4s = .75cm/s^2
Ds= 46 cm
V0=10cm/s
a=.75 cm/s^2
For the second problem there is not enough information to find the vf, Dt.we must know the 'dt to find vf.
At least one of the four equations of uniformly accelerated motion includes the variables `ds, v0 and a, for which the question gives you values. That leaves you with one unknown in your equation, which you can therefore solve for the unknown.
You should do your best to list four equations, determine which equation (or equations) include(s) `ds, v0 and a, and solve.
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