1. a) find the acceleration
A 4.0 kg shot is sped up from 6.0 m/s to 9.0 m/s by a net force of 12 N.
a) find the acceleration
b) suvat to find the distance it travels in accelerating from the initial to the final velocity.
c) Calculate the work done.
d) is this work the same as the increase in kinetic energy? (1/2mv2 - 1/2mu2 )
e) does the magnitude of the force change this result?
3.0 m/s/s
7.5 m
90. J
90. J – Yes
No – show why W

2. A 4. 0 kg shot is sped up from 6. 0 m/s to 9
A 4.0 kg shot is sped up from 6.0 m/s to 9.0 m/s by a net force of 12 N.
a) find the acceleration
a = F/m = (12 N)/( 4.0 kg) = 3 m/s/s
b) suvat to find the distance it travels in accelerating from the initial to the final velocity.
v2 = u2 + 2as, s = (v2 – u2)/(2a), s = ((9.0 m/s)2 – (6.0 m/s)2)/(2(3 m/s/s)) = 7.5 m
c) Calculate the work done.
W = Fs = (12 N)(7.5 m) = 90 J
d) is this work the same as the increase in kinetic energy? (1/2mv2 - 1/2mu2 )
1/2mv2 - 1/2mu2
1/2(4.0 kg)(9.0 m/s)2 - 1/2(4.0 kg)(6.0 m/s)2 = 90 J
So – yes it is the same
e) does the magnitude of the force change this result?
No – it does not – a smaller force would require a bigger distance, and a larger force would take a smaller distance. Fs would remain constant. Ultimately,
Fs = (ma)((v2 – u2)/(2a)) so the acceleration will cancel. W
90. J