Work and energy

1.When is work said to be done?

• a) When an object is at rest

• b) When force is applied but there is no displacement

• 
  c) When force is applied and the object is displaced in the direction of force

• 
  d) When force is applied opposite to the direction of displacement

2.Which of the following is the SI unit of work?

• a) Newton

• b) Joule

• c) Watt

• d) Pascal

3. 3.A man pushes a wall but fails to displace it. What is the work done by him?
   
   
   

• 3. a) Positive

• 3. 
     b) Negative

• 3. c) Zero

• 3. d) Infinite

4. If a body is moving with a constant velocity, what is the work done by the net force acting on it?
   
   
   

• a) Positive

• b) Negative

• c) Zero

• 
  d) Cannot be determined

The energy possessed by a body due to its motion is called:

• a) Potential energy

• 
  b) Kinetic energy

• 
  c) Mechanical energy

• d) Chemical energy

The work done by a force is positive when:

• a) The force and displacement are in the same direction

• b) The force and displacement are perpendicular

• 
  
  c) The force and displacement are in opposite directions

• 
  d) No force is applied

Which of the following has the highest kinetic energy?

• a) A moving car

• b) A rolling ball

• c) A flying bird

• 
  
  
  d) A stationary object

A force of 50 N displaces a body by 4 m in the direction of the force. The work done is:

• a) 200 J

• b) 100 J

• c) 250 J

• d) 150 J

A car of mass 1000 kg is moving with a speed of 20 m/s. How much work is required to stop the car?

• a) 2 × 10⁵ J

• b) 1 × 10⁵ J

• 
  c) 4 × 10⁵ J

• d) 5 × 10⁵ J

A ball of mass 0.5 kg is dropped from a height of 10 m. What will be its speed just before hitting the ground? (Take g=10g = 10g=10 m/s²)

• a) 10 m/s

• b) 14.14 m/s

• c) 20 m/s

• d) 40 m/s