Một xe đang chuyển động thẳng thì tắt máy, chuyển động chậm dần đều với gia tốc 2 m/s2, sau khi đi được 50m thì có vận tốc 5 m/s. a) Tính vận tốc ban đầu và thời gian xe đi hết đoạn 50 m đó.
b) Sau bao lâu thì xe dừng hẳn? Tính quãng đường xe đi được từ lúc bắt đầu hãm phanh cho đến lúc dừng.

Ablock of mass m = 2.5 kg is attached to a spring with spring constant k = 790 n/m. it is initially at rest on an inclined plane that is at an angle of 28 degrees with respect to the horizontal, and the coefficient of kinetic friction between the block and the plane is k = 0.14. in the initial position, where the spring is compressed by a distance of a = 0.18 m, the mass is at its lowest position and the spring is compressed the maximum amount. take the initial gravitational energy of the block as zero. b) if the spring pushes the block up the incline, what distance, l, in meters will the block travel before coming to rest? the spring remains attached to both the block and the fixed wall throughout its motion.

1. jay fills a wagon with sand (about 20 kg) and pulls it with a rope 30 m along the beach. he holds the rope 25° above the horizontal. the rope exerts a 20-n tension force on the wagon. how much work does the rope do on the wagon?

In the illustration, which two simple machines are being used to enable the student to reach the door? a. inclined plane and pulley b lever and wheel-and-axle c pulley and lever d wheel-and axle and inclined plane