An object of mass 20 kg
moves along a straight line on a smooth horizontal surface. A force F acts on
the object in its direction of motion.A graph of force against time is shown
here. What is the velocity of the object at t=6s if its velocity at t=4s is 4
m/s?
my options are a) 3.5 m/s b)4.5 m/s c)5.3 m./s d)6.2 m/s
my options are a) 3.5 m/s b)4.5 m/s c)5.3 m./s d)6.2 m/s
Solution
For the first 3 seconds,
the force is 20 N. For the last 3 seconds, the force decreases from 20 N to 0
N. To determine the velocity at 3 seconds, use the following equation.
Average force * time = mass * increase of velocity
The average force at first 3 second is 20N and at 2nd 3 second is 10N
Momentum =Forcextime=massxchange in velocity
Average force * time = mass * increase of velocity
The average force at first 3 second is 20N and at 2nd 3 second is 10N
Momentum =Forcextime=massxchange in velocity
20 * 3 = 20 * ∆v
∆v = 3 m/s
To determine the increase of velocity for the last 3 seconds, use the same equation. In this case the average force is 10 N.
10 * 3 = 20 * ∆v
∆v = 1.5 m/s
The final velocity is equal to the sum of these two numbers.
Final velocity = 4.5 m/s(Answer)
∆v = 3 m/s
To determine the increase of velocity for the last 3 seconds, use the same equation. In this case the average force is 10 N.
10 * 3 = 20 * ∆v
∆v = 1.5 m/s
The final velocity is equal to the sum of these two numbers.
Final velocity = 4.5 m/s(Answer)
