5.4 Mass and weight  (Page 3/5)

What is the relationship between weight and mass? Which is an intrinsic, unchanging property of a body?

How much does a 70-kg astronaut weight in space, far from any celestial body? What is her mass at this location?

Which of the following statements is accurate?

(a) Mass and weight are the same thing expressed in different units.

(b) If an object has no weight, it must have no mass.

(c) If the weight of an object varies, so must the mass.

(d) Mass and inertia are different concepts.

(e) Weight is always proportional to mass.

When you stand on Earth, your feet push against it with a force equal to your weight. Why doesn’t Earth accelerate away from you?

How would you give the value of $\overrightarrow{g}$ in vector form?

The weight of an astronaut plus his space suit on the Moon is only 250 N. (a) How much does the suited astronaut weigh on Earth? (b) What is the mass on the Moon? On Earth?

Suppose the mass of a fully loaded module in which astronauts take off from the Moon is $1.00\times {10}^4$ kg. The thrust of its engines is $3.00\times {10}^4$ N. (a) Calculate the module’s magnitude of acceleration in a vertical takeoff from the Moon. (b) Could it lift off from Earth? If not, why not? If it could, calculate the magnitude of its acceleration.

A rocket sled accelerates at a rate of ${49.0\text{m/s}}^2$ . Its passenger has a mass of 75.0 kg. (a) Calculate the horizontal component of the force the seat exerts against his body. Compare this with his weight using a ratio. (b) Calculate the direction and magnitude of the total force the seat exerts against his body.

Repeat the previous problem for a situation in which the rocket sled decelerates at a rate of ${201\text{m/s}}^2$ . In this problem, the forces are exerted by the seat and the seat belt.

A body of mass 2.00 kg is pushed straight upward by a 25.0 N vertical force. What is its acceleration?

A car weighing 12,500 N starts from rest and accelerates to 83.0 km/h in 5.00 s. The friction force is 1350 N. Find the applied force produced by the engine.

A body with a mass of 10.0 kg is assumed to be in Earth’s gravitational field with $g=9.80{\text{m/s}}^2$ . What is its acceleration?

A fireman has mass m ; he hears the fire alarm and slides down the pole with acceleration a (which is less than g in magnitude). (a) Write an equation giving the vertical force he must apply to the pole. (b) If his mass is 90.0 kg and he accelerates at $5.00{\text{m/s}}^2,$ what is the magnitude of his applied force?

A baseball catcher is performing a stunt for a television commercial. He will catch a baseball (mass 145 g) dropped from a height of 60.0 m above his glove. His glove stops the ball in 0.0100 s. What is the force exerted by his glove on the ball?

When the Moon is directly overhead at sunset, the force by Earth on the Moon, $F_{\text{EM}}$ , is essentially at $90\text{°}$ to the force by the Sun on the Moon, $F_{\text{SM}}$ , as shown below. Given that $F_{\text{EM}}=1.98\times {10}^{20}\text{N}$ and $F_{\text{SM}}=4.36\times {10}^{20}\text{N},$ all other forces on the Moon are negligible, and the mass of the Moon is $7.35\times {10}^{22}\text{kg},$ determine the magnitude of the Moon’s acceleration.