A car moving with a velocity of 20 ms-1 stopped at a distance of 40 m. If the same car is travelling at double the velocity, the distance travelled by it for same retardation is
320 m
1280 m
160 m
640 m
C.
160 m
Velocity of car (u) = 20 ms-1
Distance (s) = 40 m
From Newton's third equation,
In the second condition, the velocity becomes twice i.e, u' = 2u
Again from Newton's third equation, we get
A substance of mass 49.53 g occupies 1.5 cm3 of volume. The density of the substance (in g cm-3) with correct number of significant figures is
3.3
3300
3302
33.0
Two balls are thrown simultaneously in air. The acceleration of the centre of mass of the two balls when in air
is equal to g (acceleration due to gravity)
depends on the speeds of the two balls
depends on the masses of the two balls
depends on the direction of motion of the two balls
A body of the mass 50 kg is suspended using a spring balance inside a lift at rest. If the lift starts falling freely, the reading of the spring balance is
< 50 kg
= 50 kg
> 50 kg
= 0
The value of acceleration due to gravity at a depth of 1600 km is equal to
4.9 ms-2
9.8 ms-2
7.35 ms-2
19.6 ms-2
A motor pump lifts 6 tonnes of water from a well of depth 25 m to the first floor of height 35 m from the ground floor in 20 minutes. The power of the pump (in kW) is [g = 10 ms-2]
3
12
15
6
The angle between velocity and acceleration of a particle describing uniform circular motion is
180°
90°
45°
60°
For which combination of working temperatures, the efficiency of engine is the least ?
100 K, 80 K
40 K, 20 K
80 K, 60 K
60 K, 40 K