Question

If a flea can jump straight up to a height of 21.6cm , what is its initial speed as it leaves the ground, neglecting air resistance? how long is it in the air?

Answer 1

Consider a flea which jumps straight up to a height of 21.6cm The objective is to calculate the initial speed as the flea leaves the ground Recall the formula v =u2ah (1) Where v is the final speed, u is the initial speed and h is the height The acceleration due to gravity =-9.81 m/s The final speed of the flea when it jumps is 0 m/s Convert height from cm to m that is, 0.216 m Substitute the values in equation (1) to get, 0 u2-2x9.81x0.216 u4.2379 u 2.058 Hence, the initial speed of the flea is 2.058 m/s The objective is to calculate how long the flea is in the air The time taken to go up is given by y u+at 0 2.058-9.8 1t 2.058 9.81t t 0.209 The total time is the time to go up and come down that is, 2t 0.41800 Hence, the flea is in the air for 0.418 s