Question

A. An object of mass 10 kg is dropped from a height of 15m. Find its kinetic energy when it is half way
down.


B. When is the work done by a body said to be negative?

Answer 1

A
Here ,

kE = 1 / 2 mv^2
v^2 = 2gh
kE = 1/2 mgh
kE = 1/2 x 10 x15 x 9.8
kE = 1470 /2
KE = 735 J

B
W = f.s cosO
if the value of O is negative
as it is
Cos 180 = -1

then it means when the displacement of the object take place to the force applied then its value is neagtive .

Answer 2

Explanation:

A

Here ,

kE = 1 / 2 mv^2

v^2 = 2gh

kE = 1/2 mgh

kE = 1/2 x 10 x15 x 9.8

kE = 1470 /2

KE = 735 J

B

W = f.s cosO

if the value of O is negative

as it is

Cos 180 = -1

then it means when the displacement of the object take place to the force applied then its value is neagtive .