A balloon contains 10g of air. The air begins to escape from a small hole in the balloon at the rate of 4cms-1 and it completely shrinks in 2 seconds. What is the average force on the balloon?
5 dyne
10 dyne
15 dyne
20 dyne
What should be the tension in a rope pulling vertically upward a mass of 100 kg so that starting from rest it acquires a velocity of 4 m/s in 1.5 seconds?
1278 N
1247 N
1287 N
1894 N
A block of mass 50 kg just slides over a horizontal distance of 1 m. If coefficient of friction between their surfaces is 0.2, the work done against friction is
98 J
56 J
72 J
34 J
A string of length l fixed at one end carries a mass 'm' at the other end. The string makes around the horizontal axis through the fixed end as shown in the figure.
The tension in the string is
16 ml
4 ml
8 ml
2 ml
An explosion blows a rock into three parts. Two parts go off at right angles to each other. These two are, 1 kg first part moving with a velocity of 12 ms-1 and 2 kg second part moving with a velocity of 8 ms-1. If the third part flies off with a velocity of 4 ms-1, its mass would be
3 kg
5 kg
7 kg
17 kg
A fireman wants to slide down a rope. The breaking load for the rope is 3/4th of the weight of the man. With what minimum acceleration should the fireman slide down? Acceleration due to gravity is g.
1/4 g
1/2g
3/4g
zero
A man slides down a light rope whose breaking strength is η times his weight .What should be his maximum acceleration so that the rope does not break ?
g (1 - η)
ηg
g /1+η
g/1 - η
The upper half of an inclined plane of inclination θ is perfectly smooth while the lower is rough.A body starting from rest at the top comes back to rest at the bottom,if the coeffecient of friction for the lower half is given by
μ = sin θ
μ = cotθ
μ = 2 cosθ
μ = 2 tanθ
When milk is churned, cream gets seperated due to
Centripetal force
Centrifugal force
Frictional force
Gravitational force
A gramaphone record is revolving with an angular velocity ω. A coin is placed at a distance r from the centre of the record. The static coefficient of friction is μ. The coin will revolve with the record if
r=μgω2