Question

1) A solar collector heats the water in the water tank of a home. Which energy transformation equation best describes this situation?

a) radiant --> thermal

b) radiant --> electrical

c) radiant --> gravitational --> electrical

d) radiant --> gravitational --> thermal

2) In which case is negative work done?

a) The work done by Earth on a ball as the ball, which was initially at rest, falls 3.0 m down towards Earth.

b) A eastward force is applied to an eastward moving soccer ball that is already moving at a constant velocity to increase its speed in that direction.

c) A cart is moving at a constant velocity of 10 m/s [W] when a 0.5 N [downward] force is applied.

d) The work done by Earth on an arrow as it is fired 200 m straight up into the air.

3) An elevator motor lifts a load of 2500 kg a height of 12.0 m in 3.00 seconds. The energy required by the motor to accomplish this task is 300000 J. What is the efficiency of the elevator?

a) 10.0%

b) 98.0%

c) 102%

d) 8.17%

4) A roller coaster has two vertical loops one after the other. The roller coaster has a speed of 7.00 m/s at the top of the first loop with a height of 22.2 m. It then proceeds around the second vertical loop with a height of 15.0 m. What is the speed of the roller coaster at the top of the second vertical loop?

a) 7.00 m/s

b) 13.8 m/s

c) 8.40 m/s

d) 11.2 m/s

5) The capacity to do work is known as

a) work

b) efficiency

c) energy

d) heat

6) A person lifts a pail of water of mass of 1.50 kg from the ground to a deck, 1.00 m above the ground. How much work was done by gravitational force on the pail of water?

a) –14.7 J

b) +1.50 J

c) –1.50 J

d) +14.7 J

7) In which case is positive work done?

a) A eastward force is applied to an eastward moving soccer ball that is already moving at a constant velocity to increase its speed in that direction.

b) A cart is moving at a constant velocity of 10 m/s [W] when a 0.5 N [E] force is applied.

c) Earth applies a force on the Moon as the Moon travels one completion rotation in orbit around Earth.

d) The work done by air resistance as a baseball is thrown horizontally towards the catcher.

8) A motorboat has a power output of 32 MW and provides 4.0 MJ of energy in

a) 0.12 min

b) 0.12 s

c) 80 s

d) 80 min

Answer 1

1. (D) As solar collector concentrate heat energy from solar radiations and convert it into thermal radiations

2.(D) The arrow is fired upwards and gravitational force always acts downwards which leads to angle between force and displacement 180°

F×s×cos(180) = -Fs (Negative)

3.(B)

Work done for lifting load= 2500×12×g

W=2500×12×9.8

W=294000

Energy required= 300000

Efficiency= 294000/300000

Efficiency=0.98

Efficiency in percentage= 0.98×100= 98%

5. (C) Energy

6.(A)

Work done by gravitational force= -mgh

W= - 1.5×9.8×1

W= -14. 7 J

7. (A)Force is applied in same direction in which ball is moving.

4,8 are done below