Unit 3- Physical Science

The formula for calculating power is work divided by time (power = work ÷ time). What are two ways of stating the same relationship?

work = power × time time = work ÷ power

In a video game, a ball moving at 0.6 meter/second collides with a wall. After the collision, the velocity of the ball changed to -0.4 meter/second. The collision takes 0.2 seconds to occur. What's the acceleration of the ball during the collision? Use a= end v- starting v/t

-5.0 m/s2

A carmaker has designed a car that can reach a maximum acceleration of 12 meters/second2. The car's mass is 1,515 kilograms. Assuming the same engine is used, what should the car's mass be if the carmaker wants to reach an acceleration of 15 meters/second2? Use F = ma.

1,212 kg

Sully is riding a snowmobile on a flat, snow-covered surface with a constant velocity of 10 meters/second. The total mass of the snowmobile, including Sully, is 280 kilograms. If Sully accelerates to a velocity of 16 meters/second over 10 seconds, what's the force exerted by the snowmobile to accelerate? Use F = ma, where a= end v- starting v/t

168 N

A car moves with an average speed of 45 miles/hour. How long does the car take to travel 90 miles?

2 hours

A car accelerates from 4 meters/second to 16 meters/second in 4 seconds. The car's acceleration is _____ meters/second2.

3

Tori experiments with pulleys in physics class. She applies 70 newtons of force to a single pulley to lift a bowling ball. By adding another pulley, she'd get a mechanical advantage of 2. What's the minimum input force she'll need to lift the ball if she adds another pulley?

35 N

Carter pushes a bag full of basketball jerseys across the gym floor. Then he pushes with a constant force of 21 newtons. If he pushes the bag 9 meters in 3 seconds, how much power does he use? (Hint: 1 watt = 1 nm/s)

63 watts

Gina is driving her car to work, but she's stopped at a red light. When the light turns green, she presses the gas pedal and accelerates (speeds up) to move the car. Which of these statements is true the moment Gina presses the gas pedal? Assume the road is flat and level. A. The net force on the car is zero in the horizontal direction. B. The net force on the car is zero in the horizontal and the vertical directions. C. The net force on the car is greater than zero in the horizontal direction. D. The net force on the car is greater than zero in the vertical direction. E. The net force on the car is less than zero in the vertical direction.

C. The net force on the car is greater than zero in the horizontal direction.

Anne applies a force on a toy car and makes it move forward. What can be said about the forces acting on the toy car at the moment Anne applies the force?

The forces acting on the toy are unbalanced

Matthew throws a ball straight up into the air. It rises for a period of time and then begins to drop. At which points in the ball's journey will gravity be the greatest force acting on the ball?

When the ball leaves his hand, when it is up in the air, and when it starts to fall.

An object has one force acting on it. It is a 33-newton force pointing downward. To create a net force of zero on the object, which force must be applied to it?

a 33-newton force pointing upward

James gently releases a ball at the top of a slope, but does not push the ball. The ball rolls down the slope. Which force caused the ball to move downhill?

gravitational force

Blake and Sandra are having a rummage sale. Blake drags 3 boxes a distance of 10 meters each. He exerts a force of 20 newtons on each box. Sandra drags 4 boxes a distance of 12 meters each. She exerts a force of 15 newtons on each box. Blake takes 2 minutes to complete his work. Sandra takes 4 minutes. Blake does (more or less) work than Sandra. Blake's power is (more or less) than Sandra's power. (Hint: Use W = Fd and P=w/t)

less, more

What is the primary force that helps suspension bridges use cables to hold their spans up?

tension force