Question 2
a)Work done by friction = -30 J ( negative sign for force opposite to displacement )
b)Work done by friction is in the form of heat energy (increase in internal energy giving rise to increase in temperature )
c) zero joule ( normal force perpendicular to displacement)
d) COME : KE1 + KE1 = KE2 + PE2 + W( by friction)
Ans : v = 9.2 ms-1
Question 3
a) Acceleration = 0 , Force of motor = Total resistive forces = 900 N
Power of motor = FV = 900(70000/3600)*2= 1.8 x 10*4 W
b) Pout /Pin = 0.8
Pin =Pout / 0.8 = 2.3 x 10*4N
Question 4
b) i) Area under graph = 100 J
ii) KE = 100J
v = 10ms-1
( F = ma cannot be used for non constant force )eventhough you may get the same answer.
Question 5
a) Initial momentum = 1.5 NS (mass x velocity)
bi) Using COM : Inital momentum = Final momentum
1.5 = Mv (inelastic collison : mass of bullet + block = 2.00 kg)
v = 0.75 ms-1(common velocity of block +bullet)
bii) Using COME: KE1+PE1 = KE2+ PE2
where KE2 AND PE1 both are zero
0.5 m v2 = m g h
h = 0.0287 m
ii) No drag force on the bullet + block
Question 6
a) Reference at PE= 0 is at x = 1.0 m
b) F= -(gradient) = -(-300/4)= +75 N (to the right )
c) Force acts towards the right.
