Starting from rest, a ball of mass 2 kg is accelerated at 4 m/s^2 for 3 s. What is the final kinetic energy (in J) of the ball after 3 s?

144 joules

Explanation:

v=initial velocity+(acceleration × time)

v=0+(4×3)

v=12m/s

k.e =0.5 × mass × velocity^2

=0.5 × 2 × 12^2

=1 × 144

=144 joules

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