A Bouncing Ball Made The Problem

A ball of 1kg is dropped on the floor from a height of 8m . Every time the ball bounces back it can reach 3 4 \frac{3}{4} of its previous height. Now calculate the length of total path the ball travels before it stops.


The answer is 56.

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3 solutions

Vishal S
Jan 2, 2015

When the ball falls down, it travels 8m,6m.9/2m,...........

since the distances traveled by the ball while bouncing is in G.P.

6m,9/2m,27/8m,81/32m

We can find the distances traveled by the the ball by using the formula

sum of the infinite terms in G.P.(S) =a/1-r, where a=1st term in G.P. ,r=common ratio between the two consecutive terms

Since the ball travels two times the distance it traveled while one bouncing

therefore the distance is 2a/1-r + 8

by substituting the values, we get

Total distance traveled by the ball=2(6)/1-3/4 + 8

=12/1/4 + 8

=48 + 8

=56

therefore the total distance traveled by the ball before it comes to rest is 56

hai eclipse how are you i forgot this idea and i revealed your solution

sudoku subbu - 6 years, 5 months ago
Tony Sprinkle
Jan 4, 2015

The total distance d d the ball travels is: d = 8 m + 2 6 m + 2 9 2 m + d = 8 \text{ m} + 2\cdot6 \text{ m} + 2\cdot\frac{9}{2} \text{ m} + \cdots = 2 n = 1 8 ( 3 4 ) n 1 m 8 m = 2\sum_{n=1}^\infty 8\left(\frac{3}{4}\right)^{n-1} \text{ m} - 8 \text{ m} = 2 ( 8 1 3 4 ) m 8 m = 2\left(\frac{8}{1-\frac{3}{4}}\right) \text{ m} - 8 \text{ m} = 56 m = \boxed{56} \text{ m}

Nelson Mandela
Jan 2, 2015

coefficient of restitution is e= h 1 h \sqrt { \frac { h1 }{ h } } .

where, h1=height after 1 collision = 24/4 = 6m.

h = original height = 8m.

thus, e^2 = 0.75.

total distance travelled before the ball stops is h ( 1 + e 2 1 e 2 ) h(\frac { 1+{ e }^{ 2 } }{ 1-{ e }^{ 2 } } ) .

= 8 ( 1 + 0.75 1 0.75 ) 8(\frac { 1+{ 0.75 } }{ 1-{ 0.75 } } ) = 8 x 7 = 56 \boxed{56}

Nice explanation, but I had used G.P. for this sum

Vishal S - 6 years, 5 months ago

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