3.1 Energy Motion Force and Work

Front

To move something, use energy to exert a force.

Back

energy, force

Answer explanation

To move something, you must use energy to exert a force. Energy is required to initiate movement, while force is the action applied to change the object's state of rest or motion.

Front

Two kids push a cart: Maria north, Steven south. True statement?

Back

If the ball moves south, only Steven is doing work.

Answer explanation

If the ball moves to the south, it means Steven's force is overcoming Maria's push. Therefore, only Steven is doing work on the ball, as work is defined by the direction of force and movement.

Front

Work done pushing a 10-kg cart 5m with 20N force.

Back

100 N-m

Answer explanation

Work is calculated using the formula: Work = Force x Distance. Here, Work = 20 N x 5 m = 100 N-m. Therefore, the correct answer is 100 N-m.

Front

Unit of force measurement

Back

Newtons

Answer explanation

The unit used to measure force is Newtons. It is defined as the force required to accelerate a one-kilogram mass by one meter per second squared. Pounds measure weight, grams measure mass, and kg/m² is a unit of pressure.

Front

Work done by a motor lifting a train car 70m with a force of 15,000N.

Back

1,050,000 J

Answer explanation

Work is calculated using the formula: Work = Force x Distance. Here, Work = 15,000 N x 70 m = 1,050,000 J. Therefore, the correct answer is 1,050,000 J.

Front

Colton applied 80 N to push a nail 0.25 m in 5 s. Power used?

Back

4 w

Answer explanation

Power is calculated using the formula: Power = Work / Time. Work is Force x Distance, so Work = 80 N x 0.25 m = 20 J. Therefore, Power = 20 J / 5 s = 4 W. Thus, the correct answer is 4 W.

Front

Force and motion not in the same direction:

Back

work not done.

Answer explanation

When force and motion are not in the same direction, the angle between them is not zero. Therefore, the work done is calculated as the product of force and the displacement in the direction of the force, which results in zero work.

Front

Force and motion in the same direction...

Back

Work is done.

Answer explanation

When force and motion are in the same direction, work is done because work is defined as the product of force and the distance moved in the direction of the force. Thus, the correct answer is that work is done.

Front

Example of work done:

Back

Lifting books off a desk

Answer explanation

Lifting books off a desk involves applying a force to move the books against gravity, which qualifies as work done. In contrast, holding a backpack or pushing a wall does not involve movement in the direction of the force.

Front

A 1.0 N book is lifted 2 m.

Back

2 J

Answer explanation

Work is calculated as force multiplied by distance. Here, work = 1.0 N * 2 m = 2 J. Therefore, the correct answer is 2 J.