SECTION A
Q1. A bus of mass 500 kg is moving with a velocity of 5 m/s and is acted upon by a forward force a
500 N due to engine and retarding force of 200 N due to friction. Find the velocity of bus after 20 s.
? Why does a hackseater move forward when a fast moving bike is stooped suddenly?
Answers
Explanation:
⟶ Mass of bus = 500kg
⟶ Initial velocity of bus = 5m/s
⟶ Force due to engine = 500N
⟶ Retarding force = 200N
⟶ Time = 20s
To Find :
➾ Final velocity of bus after the given interval of time.
Concept :
➳ This question is completely based on the concept of Newton's second law of motion.
➳ As per this law, Net force acts on the moving object is defined as the rate of change of linear momentum.
Mathematically,
\bigstar\:\underline{\boxed{\bf{F=\dfrac{\Delta P}{\Delta t}}}}★
F=
Δt
ΔP
➳ Momentum is defined as the product of mass and velocity.
Calculation :
\begin{gathered}\longrightarrow\tt\:F_{net}=\dfrac{m(v-u)}{t}\\ \\ \longrightarrow\tt\:(500-200)=\dfrac{500(v-5)}{20}\\ \\ \longrightarrow\tt\:300=25(v-5)\\ \\ \longrightarrow\tt\:v-5=\dfrac{300}{25}=12\\ \\ \longrightarrow\tt\:v=12+5\\ \\ \longrightarrow\underline{\boxed{\bf{v=17\:ms^{-1}}}}\:\gray{\bigstar}\end{gathered}
⟶F
net
=
t
m(v−u)
⟶(500−200)=
20
500(v−5)
⟶300=25(v−5)
⟶v−5=
25
300
=12
⟶v=12+5
⟶
v=17ms
−1
★