Answer:
a = 1 m/s²
Explanation:
given,
mass of the person = 60 Kg
Net External force exerted = 90 N
force of friction opposing the motion = 30 N
acceleration of the box = ?
Net force = External force applied - frictional force
Net force = 90 - 30
net force = 60 N
we know
F = mass x acceleration
60 = 60 x a
a = 1 m/s²
acceleration of the box is equal to a = 1 m/s²
The time period of the pendulum is affected by the acceleration due to gravity. The tension does not have any effect on the time period of the pendulum and also the mass of the bob does not effect the time period of the pendulum.

Hence, if the gravity increases then the time period of the pendulum will decreases and it will swing faster.
The substance that is made of atoms of more than one type bound together is called an atomic bond or a multi bond
Let the mass of 2500 kg car be
and it's velocity be
and the mass of 1500 kg car be
and it's velocity be
.
After the bumping the mass be M and it's velocity be V.
By law of conservation of momentum we have

2500 * 5 + 1500 * 1=4000 * V
V = 14000/4000 = 7/2 = 3.5 m/s
So the velocity of the two-car train = 3.5 m/s
Electrification is widely considered as a viable strategy for reducing the oil dependency and environmental impacts of road transportation. In pursuit of this strategy, most attention has been paid to electric cars. However, substantial, yet untapped, potentials could be realized in urban areas through the large-scale introduction of electric two-wheelers.