Question

A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 metric tonnes (Hint: 1 metric tonne = 1000 kg).

Answer 1

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• Initial velocity, u = 0 (since the truck is initially at rest)
• Distance travelled, s = 400 m
• Time taken, t = 20 s
• According to the second equation of motion:
• s=u + 1/2 at square
• Where
• Acceleration = a
• 400 = 0 + 1/2 a (20)sq
• 400 = 1/2 a (400)
• a = 2m/s sq
• 1 metric tonne = 1000kg
• Therefore 7 metric tonnes = 7000kg
• Mass of truck, m = 7000 kg
• From Newton’s second law of motion:
• Force, F = Mass × Acceleration
• F = ma = 7000 × 2 = 14000 N

• Hence, the acceleration of the truck is 2 m/s2 and the force acting on the truck is 14000 N.

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Answer 2

Answer:

The truck starts from rest, so initial velocity = 0

Distance travelled = 400 m

Time taken = 20 s

We know the equation of motion, S = ut + ½ at2

400 = 0 + ½ a * (20)2

a = 2 m/s2

Now, mass = 7 metric tonnes

= 7 * 1000

= 7000 kg

So force = mass * acceleration

F = 7000 * 2

= 14000 N

Explanation: