A truck is moving with speed of 54 km/h. Truck’s driver applied brakes suddenly and brings the truck to rest in 5 sec. What is the average retarding force on truck, if the mass of the truck and driver is 400 kg?
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Answer
- Retarding force on truck is " 1200 Newtons "
Given
- A truck is moving with speed of 54 km/h. Truck’s driver applied brakes suddenly and brings the truck to rest in 5 sec
To Find
- Average retarding force on truck, if the mass of the truck and driver is 400 kg
Formula Used
- 1st equation of motion
- v = u + at
- Newton Second's Law
- F = ma
Solution
Initial velocity , u = 54 km/h = 54 × ⁵/₁₈ m/s = 15 m/s
Final velocity , v = 0 m/s [ ∵ Finally goes to rest ]
Time , t = 5 s
Acceleration , a = ? m/s²
Apply 1st equation of motion .
⇒ v = u + at
⇒ 0 = 15 + a(5)
⇒ 5a = - 15
⇒ a = - 3 m/s²
- ve sign denotes retardation , which is opposite to acceleration .
Mass , m = 400 kg
Acceleration , a = - 3 m/s²
A/c Newton's Second Law ,
⇒ F = ma
⇒ F = 400 × - 3
⇒ F = - 1200 N
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