Question

C. Attempt any four questions.
1
A train starts from rest and accelerates uniformly for 20 seconds to attain a velocity of 90 km/h. It travels at
constant velocity for 15 minutes. The driver applies brakes to stop the train in next 5 seconds. Find the total
displacement of the train.
2
An object starts from rest and travels 20 meter in first 2 seconds and 160 meter in next 4 seconds. Find its
velocity 7 seconds after the start.
3
An object is dropped from rest at a height of 150 m and simultaneously another object is dropped from rest at
a height of 100 m. What is the difference in their height 2 s later, if both the objects drop with same
acceleration? How does difference in heights vary with time?
4 A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20
s. Find its acceleration. Find the force acting on it if its mass is 7 metric tonnes
5. A bullet of mass 20 g moves with a velocity of 200 m/s and gets embedded in a stationary wooden block of
mass 980 g. With what velocity will the block move?
6. A bullet of mass 10 g traveling horizontally with a velocity of 150 m/s strikes a stationary wooden block and
comes to rest in 0.03 s. Calculate the distance of penetration of bullet into the block. Also calculate the
magnitude of force exerted by the bullet on the wooden block.
(Section-B Chemistry​

Answer 1

Answer:

1. during acc.

v=u+at

90kmph=25m/s

25=0+a×20

a=1.25

S=ut+ 1/2at^2

S=0t+ 1/2(1.25×400)

S=250m

during const. velo.

15m=900s

900×25=22500m

during breaking

v=u +at,v=0,

0=25-a×5

a=5

v^2-u^2=2as

s=525/2×5=62.5m

add all 3 S

2.S=ut+ 1/2at^2

20=0+1/2(4×a)

a=10m/s^

v=0 +10×2=20m/s

S=ut+ 1/2at^2

160= 0+1/2(a×16)

a=20

v=20+20×5=120m/s

t=5 bcs taking for 7 second

3.they have 50m diff. in height

now

S=ut+ 1/2at^2, t=2

S=0 + 1×2×10×4=20

distance won't wary with time as they have same initiall speed and acc.

4.S=ut+ 1/2at^2

400=0 +1/2a×400

a=2

F=ma=7000×2=14000N