Question

C. A 75 lb (34 kg) boy falls out of a tree from a height of 10 ft (3 m). (3 points)

i. What is the kinetic energy of the boy when he hits the ground? Round your answer to the nearest joule. (1 point)

ii. What is the speed of the boy when he hits the ground? Round your answer to two significant figures. (1 point)

iii. Using the conversion factors of 1 m = 1.094 yd and 1 mi = 1760 yd, calculate the speed of the boy in miles per hour when he hits the ground. (1 point)

Answer 1

(I) kinetic energy of the boy when he hits the ground =potential energy

I. e ½mv²=mgh where g is 10ms-²

m=34kg, g=10ms² , h=3m

=34×10×3

=1020j

(i i) v²=u²+2gh

v²=0²+2×10×3

= 60

v=sqrt of 60