## Book Store

Download books and chapters from book store.
Currently only available for.
CBSE Gujarat Board Haryana Board

## Previous Year Papers

Download the PDF Question Papers Free for off line practice and view the Solutions online.
Currently only available for.
Class 10 Class 12
A body of mass 0.40 kg moving initially with a constant speed of 10 m s–1 to the north is subject to a constant force of 8.0 N directed towards the south for 30 s. Take the instant the force is applied to be = 0, the position of the body at that time to be = 0, and predict its position at t = –5 s, 25 s, 100 s.

Given,

Mass of the body, m = 0.40 kg

Initial speed of the body, u = 10 m/s, due north

Force acting on the body, F = –8.0 N

Acceleration produced in the body, a =

(i)

At
t = –5 s,

Acceleration, a' = 0

Initial velocity,
u = 10 m/s

Using the relation,

s = ut + (1/2) a' t

= 10 × (–5) = –50 m

(ii)

At
t = 25 s

Acceleration, a'' = –20 m/s2

Initial velocity, u = 10 m/s

USing the relation,

s' = ut' + (1/2) a" t2

= 10 × 25 + (1/2) × (-20) × (25)

= 250 - 6250

= -6000 m

(iii)

At
t = 100 s,

For 0 ≤ t ≤ 30 s

Acceleration, a = -20 ms-2

Initial velocity, u = 10 m/s

Now, using the equation of motion, we have

s1 = ut + (1/2)a"t

= 10 × 30 + (1/2) × (-20) × (30)2

= 300 - 9000

=  -8700 m

For 30 < t ≤ 100 s,

For t= 30 sec, as per the first equation of motion final velocity is given as,

v
= u + at

= 10 + (–20) × 30

= –590 m/s

Velocity of the body after 30 s = –590 m/s

For motion between 30 s to 100 s, i.e., in 70 s:

s2 = vt + a" t

= -590 × 70

= -41300 m

∴ Total distance, s" = s1 + s2

= -8700 -41300

= -50000 m

= -50 km.
303 Views

When the branches of an apple tree are shaken, the apples fall down. Why?

The apple fall from an apple tree when it shaken because of inertia of rest. Apple is in a state of rest and when the tree is suddenly shaken, apples still tends to remain in it's same state of rest whereas branches move.

So, the apples fall down.
1475 Views

What is Aristotle’s law of motion?

Aristotle’s law of motion states that an external force is required to keep the body in motion.
2445 Views

Define inertia.

The property by virtue of which the body cannot change its state of rest or uniform motion in a straight line, unless an external force is acting on the body is called as Inertia.
1316 Views

State Galileo’s law of motion.

Galileo’s law of motion states that, a body continues to move in the same direction with constant speed, if no force is acting on the body.
1332 Views

Is Aristotle’s law of motion now correct?

No. Aristotl'e law of motion is false.
1233 Views