Question

PHYSICS
Which of the following is not used to reduce friction (1)
a using ball bearing
busing grease between contact surfaces
cusing oil between contact surfaces
d. making scratches on the contact surfaces
2
What is the total momentum of a bullet and a gun before firing? (1)
3
A 8000 kg engine pulls a train of 5 wagons, each of 2000 kc along a horizontal track. It
the engine exerts a force of 40000 N and the track offers a frictional force of 5000 N.
then calculate: (5)
a the net accelerating forces
h the acceleration of the train and
c the force of wagon 1 on wagon 2.​

Answer 1

1. d
2. ????
3. ????

sorry for only one ans

Answer 2

1.Making scratches on the contact surfaces(d)

2.Zero is the total momentum of the system before the bullet is fired

3.Mass of the engine = 8000 kg 

Mass of each wagon = 2000 kg, 

Np. of wagons = 5 

Total mass of train = 8000+2000×5= 18000 kg 

Force, F = 40000 N 

Track resistance , R = 5000 N 

Total accelerating force = F −R =40000−5000=35000 N 

Let acceleration = x m/s² 

Acceleration , = Accelerating force / mass 

x=35000/18000= 35/18=1.94 m/s² 

Frictional resistance of 4 wagons = 5000×(2000×4)/18000 =2222 .22 N 

Accelerating force on 4 wagons =2000×4×1.944 =15552 N 

Hence total force exertred by wagon on wagon 2= Accelerating force +Frictional resistance 

=2222 .22 +15552=17774.22 N 

Total force required to produce acceleration is 17774.22 N