Force of gravity on an object = (mass of the object) x (acceleration of gravity)
12.0 Newtons = (mass of the object) x (9.8 m/s²)
Mass of the object = (12.0 Newtons) / (9.8 m/s²)
Mass of the object = 1.22 kilograms
Explanation:
It is given that,
Mass of the football player, m = 92 kg
Velocity of player, v = 5 m/s
Time taken, t = 10 s
(1) We need to find the original kinetic energy of the player. It is given by :


k = 1150 J
In two significant figure, 
(2) We know that work done is equal to the change in kinetic energy. Work done per unit time is called power of the player. We need to find the average power required to stop him. So, his final velocity v = 0
i.e. 

P = 115 watts
In two significant figures, 
Hence, this is the required solution.
The first one is an opinion though the second could be too it is for sure the first
Given :
An object 50 cm high is placed 1 m in front of a converging lens whose focal length is 1.5 m.
To Find :
the image height (in cm).
Solution :
By lens formula :

Here, u = - 100 cm
f = 150 cm

Now, magnification is given by :

Therefore, the image height is 3 m or 300 cm.