A hammer weighing 3 kg, moving with a velocity of 10 m/s, strikes the head of a spike and drives it into a block of wood. If the hammer comes to rest in 0.025s, the average (retarding) force acting on the spike will be ____.
600 N
-600 N
1200 N
-1200 N
Starting from rest, a body sides down a 450 inclined plane in twice the time it takes to slide down the same distance in the absence in the absence of friction. The coefficient of friction between the body and the inclined plane is ____.
0.33
0.25
0.75
0.80
The total mass of an elevator, with a 80 kg man in it, is 1000 kg . This elevator moving upward with a speed of 8 m/s is brought to rest over a distance 16 m. Then tension T in the cable supporting elevator is ____.
3200 N
5400 N
6500 N
7800 N
A body moves along circular path of radius 10 m and the coefficient of friction is 0.5. What should be its angular velocity in rad/s if it is not to slip from the surface?
(g = 9.8 m/s2)
0.1
0.7
5
10
An insect is crawling up a fixed hemispherical bowl of radius R if the coefficient of friction is 1/3, then the height up to which insect can crawl is ____.
2 % of R
3 % of R
4 % of R
5 % of R
If you are asked to push an object so that the acceleration produced in it is now twice as before, then the force required will be ___.
twice as before
half as before
same as before
four times as before
Internal force ____.
are always balanced
are never balanced
may or may not be balanced
None of the above
/
2.5 m/s2
0.25 m/s2
5 m/s2
0.5 m/s2
A rocket of initial mass 6000 kg ejects mass at a constant rate of 16 kg/sec with constant relative speed of 11 km/s. What is the acceleration of the rocket a minute after the blast? (Neglect gravity)
28.7 m/s2
34.9 m/s2
39.4 m/s2
27.8 m/s2
A 6000 kg rocket is set for vertical firing. If the exhaust speed is 1000 m/s, how much gas must be ejected each second to supply the thrust needed to overcome the weight of the rocket?
22.2 m/s
37.6 kg/s
58.8 kg/s
None of these