PHY101 GDB 1 Solution and Discussion

[zareen]

Assignment # 1
Semester: FALL 2019
Physics (PHY101) Total Marks: 25
Due Date:
19th November, 2019

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Question No. 1 (Marks=5 x 3=15)

1. Is it true or wrong to say that an object with zero acceleration has velocity? Either yes or no explicate it with example.
2. Can we say that an object with zero velocity have acceleration? Either yes or no explicate it with example.
3. Is it wrong or correct to say that, if an object has constant acceleration, it has a constant velocity? Either yes or no explicate it with example.

Question No. 2 (Marks=10)
Estimate the soccer ball‘s speed immediately after being kicked off if its mass is 0.5Kg as shown in the given figure.

[zareen]

1. Is it true or wrong to say that an object with zero acceleration has velocity? Either yes or no explicate it with example.

• Ans: . The velocity and acceleration of a particle do not depend on each other (however rate of change of velocity with respect to time gives acceleration ) i.e if velocity is zero acceleration may or may not be zero or vice versa.
• Example :
  Consider a simple example when we start a vehicle, initially we have zero velocity but have non-zero acceleration(that is why vehicle will start moving).
  2.If we drop a ball from some height above the earth surface the velocity at that instant is zero but acceleration in non zero (gravity) which acts downward. The acceleration would increase the velocity in some time.

3. Can we say that an object with zero velocity have acceleration?
   Either yes or no explicate it with example.

• Ans: Yes, an object can have zero velocity and still be accelerating simultaneously.
  Example:
  Consider an object moving in the forward direction. suddenly a force actson it and tries to acceleration the object in the backward direction . when you observe the object, you will find that the object will continue to move forward for some time and then stops momentarily. Then the object will start to move in the backward direction.

3. Is it wrong or correct to say that, if an object has constant acceleration, it has a constant velocity? Either yes or no explicate it with example.

• Ans: An object with a constant acceleration should not be confused with an object with a constant velocity.
  If an object is changing its velocity whether by a constant amount or a varying amount then it is an acceleration object. And an object with a constant velocity is not accelerating.

Q.2 Estimate the soccer ball‘s speed immediately after being kicked off if its mass is
0.5Kg
Ans:

F=256N
Distance =0.2M
Mass =0.5KG
Velocity=?
FORMULA:F=ma
As we know acceleration is equal to a =∆𝒗/∆𝒕
F=m(=∆𝒗/∆𝒕)
256=0.5(velocity time)
Velocity = 256 / 0.5×time
Velocity = 256 / 0.5×1
Velocity = 512km/s