ENERGY PRE TEST

How much work is required to lift a 2 kg mass to a height of 10m? (Round Answer)

• 5 J

• 20 J

• 100 J

• 200 J

Answer explanation

To calculate the work, use the formula: work = force x distance. Since the mass is lifted vertically, the force is equal to the weight of the mass. The weight can be calculated using the formula: weight = mass x gravity. Therefore, work = weight x distance. Plugging in the values, work = (2 kg x 9.8 m/s^2) x 10 m = 196 J. Rounding to the nearest whole number, the work required is 200 J. Therefore, the correct answer is 200 J.

A machine is able to do 30 J of work in 6 Sec. The power developed by the machine is?

• .20 W

• .50 W

• 5 w

• 180 w

Answer explanation

The power developed by the machine is 5 W because power is calculated by dividing the work done (30 J) by the time taken (6 sec).

Car A and Car B of equal mass travel up hill. Car A travels up the hill in half the time of car B. Compared to the power output of car B the power output of Car A is:

• The same

• Twice as much

• Half as much

• Four times as much

Answer explanation

Car A has twice the power output compared to Car B because it travels up the hill in half the time.

During a soccer game, which term best represents a quantity that has both magnitude and direction when a player kicks the ball?

• work

• power

• distance

• force

Answer explanation

Force is the term that best represents a quantity with both magnitude and direction when a player kicks the ball. It is a measure of the push or pull applied to an object.

What is the total work done by the boy in pushing a wagon 4 M with a constant force?

• 5 J

• 7.5 J

• 120 J

• 180 J

Answer explanation

The total work done by the boy in pushing the wagon 4 M with a constant force is 120 J, which is the correct choice.

At which position is the kinetic energy of the pendulum bob least?

• A

• B

• C

• D

Answer explanation

The kinetic energy of the pendulum bob is least at position D because it has the lowest velocity.

Assuming no frictional loss, what will be his kinetic energy at the bottom of the slope?

• 1,500 J

• 7,500 J

• 15,000 J

• 75,000 J

Answer explanation

The correct choice is 15,000 J because at the bottom of the slope, the kinetic energy is equal to the potential energy at the top, which is 15,000 J.

At which position is the sum of the potential and kinetic energy of the cart the same?

• A & B ONLY

• B & C ONLY

• C & D ONLY

• All positions A through D

Answer explanation

The sum of potential and kinetic energy is the same at all positions A through D.

Which block will gain the most gravitational potential energy?

(P.E._G=m X g X h)

• A

• B

• C

• D

Answer explanation

Block B will gain the most gravitational potential energy because it has the highest height, which directly affects the potential energy according to the formula P.E.G = m X g X h.

If the speed of an object is doubled, its kinetic energy will be

• halved

• doubled

• quartered

• quadrupled

Answer explanation

When the speed of an object is doubled, its kinetic energy will be quadrupled. This is because kinetic energy is directly proportional to the square of the speed.