PS7 T10L1 Quiz

If you are on a school bus with your class mates traveling at 50 miles per hour, what is a reference point that you can use to argue you are not moving?

• The road

• The seat in front of you

• The sun

• A tree outside

Satellites circle the Earth instead of floating out into space because of gravity. Which of the following describes gravity

• Gravity is a push

• Gravity is a contact force

• Gravity is always a net force

• Gravity is a non-contact force

You push a box across the floor. The force of friction between the box and the floor makes the job harder. What is true about Friction?

• Friction is a contact force

• Friction is always a pulling force

• Friction acts in the same direction as your push

• Friction is always greater than the push on the box

Two friends are playing tug o' war. Angel is pulling to the left and Jim is pulling to the right. If the rope starts to move to the left, what do you know?

• Jim and Angel are evenly matched

• There is a net force

• Jim is going to win

• There is a balanced force

If a tow truck pulls a car with 250 Newtons and the friction of the car is 150 N what is the Net force

• 400 Newtons

• 0 Newtons

• 100 Newtons

• The forces are balanced

A push or pull exerted on an object is:

• force

• acceleration

• velocity

• Newton

The combination of all forces acting on an object

• acceleration

• net force

• velocity

• Newton

Mr. Wang works in a recycling center. Recyclable materials arrive at the center mixed together. Workers use magnets to separate steel cans from other items. Which statements is true about the force between a steel can and a magnet?

• Gravity pushes the can toward the magnet.

• The force between the can and the magnet is a noncontact force.

• The attraction between the can and the magnet is a push.

Answer explanation

The pull between a magnet and an object containing iron, such as a steel can, is an example of a noncontact force. This force exerts a pull whether or not the objects touch. Gravity is another example of a noncontact force, but it occurs because of the mass of the objects, not because of magnetism.

Keisha has two large dogs and a small dog. The dogs like to play tug-the-rope together. Each of these three diagrams shows one way that the dogs play together with the rope. Look at each arrow and the number that goes with it. They show the direction and amount of force each dog exerts on the rope.

Look at the middle diagram, where the large dog and the small dog tug on the rope. Which statement correctly explains the amount and direction of the net force acting on the rope, and which direction the rope will move?

• The net force is 8 N to the left, and the rope will move to the right.

• The net force is 8 N to the left, and the rope will move to the left.

• The net force is 32 N to the left, and the rope will move to the left.

• The net force is 32 N to the right, and the rope will move to the right.

Answer explanation

The net force is the sum of all the forces acting on an object. Objects move in the direction of the net force. Same direction forces add together, while opposite direction forces subtract. Since the large dog pulls with 20N and the small dog pulls in the opposite direction with 12N, the net force will be 20N - 12N = 8N, towards the large dog on the left.

What happens to an object when balanced forces act on it?

• It accelerates in one direction
• It remains at rest or moves at a constant speed
• It changes direction
• It stops moving