Question

A ball is thrown up with a kinetic energy of 20 j. if it reaches a maximum height of 1m, find the mass of the ball

Answer 1

According to the law of conservation of energy,
Kinetic energy= Potential energy

Therefore,

KE= mgh
20= 1 × 10 × h. {considering that g=10m/s²}
h= 20÷2
h= 10 m

Answer 2

Answer:

2kg

Explanation:

K.E= 20J

K.E=1/2mu^2

u^2=( 2 × K.E)/ m

m=(2× K.E)/ u^2...... (I)

Now,

since it reaches a maximum height of 1m

v^2= u^2 - 2gh

0^2= u^2 - 2g(1)

0 = u^2 - 2g

u^2 = 2g.....(II)

Put the value of u^2 in equation (I)

m=(2 × K.E)/2g

Now, Since K.E=20 & g=10 insert the values:

m=(2 × 20) / 2 × 10

m = 2kg