When two springs A and B with force constants kA and kB are stretched by the same force, then the respective ratio of the work done on them is
kB : kA
kA : kB
kA : kB : 1
In elastic collision
both momentum and kinetic energy are conserved
neither momentum nor kinetic energy is conserved
only momentum is conserved
only kinetic energy is conserved
A spring stores 1 J of energy for a compression of 1 mm. The additional work to be done to compress it further by 1 mm is
1 J
2 J
3 J
4 J
A crate is pushed horizontally with 100 N across a 5 m floor. If the frictional force between the crate and the floor is 40 N, then the kinetic energy gained by the crate is
200 J
240 J
250 J
300 J
An engine pumps out water continuously through a hose with a velocity v. If m is the mass per unit length of the water jet, the rate at which the kinetic energy is imparted to water is
mv3
The position of a particle of mass 4 g, acted upon by a constant force is given by x = 4 t2, where x is in metre and t in second. The work done during the first 2 s is
128 mJ
512 mJ
576 mJ
144 mJ
C.
576 mJ
The position of a particle
The distance in first 2 s
x = 4t2 + t = 4 × (2)2 + 2
x = 18 m
The work done during the first 2 s
W = F . x
= m . a . x
= 4 × 10-3 × 8 × 18
W = 576 mJ
The shape of the curve representing the relation between the speed and kinetic energy of a moving object is
parabola
ellipse
straight line with positive slope
straight line with negative slope