A car of mass 1200 kg is moving along a straight line with a uniform velocity of 90 kmph. Its velocity is slowed down to 18 kmph in 4 s by an unbalanced external force. Calculate the change in momentum and the magnitude of the force required. [3 MARKS]
A car of mass 1200 kg is moving along a straight line with a uniform velocity of 90 kmph. Its velocity is slowed down to 18 kmph in 4 s by an unbalanced external force. Calculate the change in momentum and the magnitude of the force required. [3 MARKS]
Acceleration Calculation: 1 Mark
Formula application: 1 Mark
Calculation of Momentum: 1 Mark
Step 1: Calculate the acceleration of the car , convert units to metre per second.
Initial velocity of the car ,u=90 kmh−1=25 ms−1
Final velocity of the car ,v=180 kmh−1=5 ms−1
Time taken, t =4s
Acceleration ,a = ?
We know that; v=u+at
5=25+a×4
a×4=−20
⇒a=−5 ms−2
Step 2: Calculate the change in momentum
p =m(v−u)=1200(5−25)=1200×(−20)=−24000 Ns (Ns is newton second)
Step 3: Calculate the magnitude of force
Magnitude of Force(F)=m(v−u)t=−6000 N
Acceleration Calculation: 1 Mark
Formula application: 1 Mark
Calculation of Momentum: 1 Mark
Step 1: Calculate the acceleration of the car , convert units to metre per second.
Initial velocity of the car ,u=90 kmh−1=25 ms−1
Final velocity of the car ,v=180 kmh−1=5 ms−1
Time taken, t =4s
Acceleration ,a = ?
We know that; v=u+at
5=25+a×4
a×4=−20
⇒a=−5 ms−2
Step 2: Calculate the change in momentum
p =m(v−u)=1200(5−25)=1200×(−20)=−24000 Ns (Ns is newton second)
Step 3: Calculate the magnitude of force
Magnitude of Force(F)=m(v−u)t=−6000 N
