The block A is moving downward with constant velocity v0. Find the velocity of the block B, when the string makes an angle θ with the horizontal.
When two objects are connected by a string component of velocity along the string remains equal.
v1 cosθ = v 0
⇒v1= v0/ cosθ
Which of the following option is correct regarding given statements :-
(I) It is possible for an object to have motion in the absence of forces on the object.
(II) It is possible to have forces on an object in the absence of motion of the object.
Statement I is correct because in absence of force object can move with constant velocity.
Statement II is correct because if many forces act on an object such that resultant is zero, the object will be in static equilibrium
An object experiences no acceleration which of the following can NOT be true for the object
If only one force acts on the object it will be the net force. So the object will accelerate and it can't be at rest
In a general debate on topic “normal reaction and mg never form action and reaction pair” a number
of students took part :-
(I) Navneet said – Action and reaction forces should be of same nature
(II) Anand said – Action and reaction forces act on two different bodies here, normal reaction and mg both are acting on the block.
(III) Meenakshi said – Action and Reaction forces balance each other. So, normal reaction and mg should be action and reaction pair.
Mark correct option as your judgement
The correct option is:
(II) Anand is correct.
Explanation:
Action and reaction forces act on two different bodies, as per Newton's third law. Normal reaction and gravitational force (mg) both act on the same block, so they cannot form an action-reaction pair.
Acceleration of the block is :
Horizontal component of force is F cosθ = 20√2 cos 45° = 20√2 × 1/√2 = 20 N.
So, Horizontal acceleration = 20N / 10kg = 2m/s²
A hammer of man 1 kg moving with a speed of 6 m/sec strikes a wall and comes to rest in 0.1 sec find average retarding force that stops the hammer :
According to Newtons second law of motion, Force is time rate of change in momentum.
So, F = change in momentum / time
F= m (vf-vi)/t= 1 kg (0-6)/0.1= -60 N
A 5 kg block is resting on a frictionless plane, it is struck by a Jet, releasing water at the rate of 4 kg/sec emerging with a speed of 5 m/sec. Calculate the initial acceleration of block :
Force acting on the object is F = v.(dm/dt)= 5×4 = 20 N
so Acceleration is a= F/m = 20/5 = 4 m/s²
A body of mass 1 kg is acted upon by two perpendicular forces of 8 N and 6 N, find the magnitude of acceleration :
Resultant force on the object will be F= (8² + 6²)½= 10 N
So, acceleration is a = F/m = 10/1 = 10 m/s²
A small block slides without friction down an inclined plane starting from rest. Let Sn be the distance travelled from time t = n – 1 to t = n. Then Sn/Sn+1 is :
Sn = u + a/2(2n-1) = a/2(2n-1)
Sn+1 = u + a/2(2(n+1)-1) = a/2(2n+1)
Sn / Sn+1 = (2n-1)/(2n+1)
Two blocks of masses 1 kg and 2 kg are connected with massless spring as shown. If the acceleration of 1 kg block is 1 m/s² towards right then the acceleration of 2 kg block is:
Spring force acting on 1 kg block is F = m.a = 1 N
Same spring force will act on 2 kg block in opposite direction. Thus net force acting on 2 kg block is 5N - 1 N = 4N
Acceleration of the block will be 4 N/2 kg = 2 m/s²