Newton's First and Second Laws of Motion

A cart is acted on by a 5-N force forward, a 7-N force backward, and another 2-N force forward. Which statement is true about the motion of the cart?

• The cart must remain at rest.

• The cart must remain in motion in a straight line at a constant, non-zero speed.

• The cart must be keeping its velocity constant, even if its velocity is zero.

• The cart must have a velocity that is changing.

• No statement can be made about what the motion of the cart must be.

A cart is remaining at rest, and is acting under the action of a person pushing forward with 6.5 N of force, a friction force of 2.5 N pushing backward, and a third unknown force. The unknown force must be ___.

• 6.5 N forward

• 4.0 N backward

• 4.0 N forward

• 9.0 N forward

• 9.0 N backward

Newton's First Law of Motion says that an object that is acting under the influence of forces that are balanced ___.

• must be moving with a constant velocity in a straight line

• must be changing its velocity

• must be at rest

• is keeping its velocity constant, even if the velocity is zero

• might have any type of motion

A cart is acted on by a 14-N force forward, a 6-N force backward, and another 6-N force backward. Which statement is true about the motion of the cart?

• The cart must remain at rest.

• The cart must remain in motion in a straight line at a constant, non-zero speed.

• The cart must be keeping its velocity constant, even if its velocity is zero.

• The cart must have a velocity that is changing.

• No statement can be made about what the motion of the cart must be.

Camille launches has a catapult that changes the velocity of a ball (m= 2 kg) from 0 to 10 m/s in one sec. What is the average force that is exerted on the ball during launch?

• 20 N

• 5 N

• 8 N

• 0.2 N

If a 6.0-kg object is accelerating forward at 1.5 m/s², the net force on the object must be ___.

• 7.5 N

• 9.0 N

• 4.0 N

• 4.5 N

• 9.0 m/s²

A cart is moving forward at 5.0 m/s, and is acting under the action of a person pushing forward with 3.0 N of force, a friction force of 4.5 N pushing backward, and a third unknown force. The unknown force must be ___.

• 1.5 N forward

• 1.5 N backward

• 7.5 N forward

• 7.5 N backward

• 3.0 N forward

If forces on an object are balanced, what is the net force equal to?

• Zero

• The force of gravity

• The support force opposing gravity

• There is not enough information to determine the net force.

"If we apply a ___________ to an object, its __________________ will change and it will  ______________."

• force, accelerate, gravity
• accelerate, inertia, gravity
• force, velocity, accelerate
• velocity, gravity, inertia

A 5.0-kg box is under the influence of a 24.0-N force forward and a 9.0-N force backward. The acceleration of the box will be ___.

• 15 m/s² forward

• 3.0 m/s² backward

• 3.0 m/s² forward

• 15.0 m/s² forward

• 3.0 N forward