Apole vaulter at the top of his vault is 6.15 m in the air . if he has a gravitational potential energy of 4o42 j , what is his mass?

Gravitational potential energy is given by 

 U=mgh

 where 

 m is the mass of the object 

 h is the height of the object above the ground (Earth's surface)

 g is the gravitational acceleration constant, 9.8ms2.

 For h=6.15m and U=4042J, we can rearrange to solve for m:

 m=U/gh

 m=(4042J)/((9.8m/s^2)*(6.15m))

 m=67.06 Kg

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s