A motorcar of mass 1200Kg is moving along a straight line with a uniform velocity of 90 km/hr. Its velocity is slowed down to 18 km/hr in 4 sec by an unbalanced external force. Calculate the acceleration and change in momentum also calculate the mangitude of the force required.
Answers
ANSWER :
ACCELERATION : It is defined as rate of change of velocity per unit time.
ACCELERATION = Final Velocity ₋ Initial Velocity / Time.
S.I Unit = m/s²
MOMENTUM : It is defined as product of mass and velocity. It is represented by letter P. Given by P = m × v, where m is mass and v is a velocity.
S.I Unit : kg⋅m/S
- Here mass of motor car, ( m ) = 1200 kg
Initial velocity of car, ( u ) = 90 km/h = 90 × 5/18 m/s
= 25m/s
Final velocity of a car, ( v ) = 18 km/h = 18 × 5/18
= 5 m/s
And Time ( t ) = 4s
Acceleration a = v ₋ u / t = 5 - 25 / 4 = ₋ 5m/s²
Change in momentum of car
mv - mu = m ( v - u )
= 1200 ( 5 - 25 )
= - 24000 kg m/s
Magnitude of force F = ma
= 1200 × ( ₋ 5 )
= ₋ 6000N
Negative sign of acceleration, charge in momentum and force suggests that the force is opposing the motion of motor car.