Question

42. Two balls are released from a height of 20m at an interval of 1 sec. What would be the distance between them after 2 sec ? (a) 24.5 m (c) 9.8 m (d) 19.6 m (b) 4.9 m​

Answer 1

Answer:

Class 11>>Physics>>Motion in a Straight Line>>Problems on Equation of Motion>>A body released from a height falls free

Question

A body released from a height falls freely towards the earth. Another body is released from the same height exactly a second later. Then the separation between the two bodies two seconds after the release of the second body is

Solution

Both the bodies are falling freely with acceleration g=9.8 m/s2.

Equation to be used: s=21×g×t2

The first body descends for 3 sec. 

The height covered by this body is s1=21×(9.8)(32)=44.1 m

The second body descends for 2 sec. 

The height covered by this body is s2=21×(9.8)(22)=19.6 m

Separation between the bodies is s1−s2=(44.1−19.6)=24.5 m

Answer 2

Answer:

(A) 24.5 m

Explanation:

Distance travelled by the ball in time t is given by S = ut + 1/2 gt².

Now, the distance between them after 2 sec will be = 1/2g(3)²-1/2g(2)² [Where u = 0]

= 1/2g(9-4) metres

= 4.9×5 [g = 9.8m/s²] metres

= 24.5 metres [Ans]